VERSIONS
--------
02.2.2  -  In wrapper of deco'd function:
           Expose a method log_message(msg)
           which knows the current indent amount and automatically
           indents properly.
           Useful for verbose debugees that want their blather
           to align properly. Developed for noconflict3,
           findings transported to the metaclass example
           in test_log_calls.py and docs log_calls.* and readme.*.
           Added sections to docs on log_message(),
           and final section on how functions & methods access
           their deco'd wrapper & thus the attributes added for them
           by log_calls. Revised links to full doc in readme
           to point to htmls on pythonhosted.org.

0.2.1   -  First row of history_as_csv: NO QUOTES.
           The quotes were part of the column names in Pandas!
           so that if you made a DataFrame df from the csv,
           you'd have to access e.g. the retval column as:
                 df["'retval'"]
           Further, because 'retval' isn't a valid Python identifier,
           you couldn't use the column names as attributes
           of the DataFrame.
           Added attribute to stats: history_as_DataFrame,
           returns a DataFrame if Pandas is installed (importable),
           else returns None.

0.2.0   -  Renamed "call_history" and "call_history_as_csv"
           attributes of the stats attribute
           ->
           "history", "history_as_csv", as what other kind of
           history would there be.

0.1.14  - (*) Factored out a (fat) base class for log_calls,
              also the base class for new decorator record_history
          (*) record_history required/inspired "visible" bool
              attribute for DecoSetting objs
          (*) added support for it throughout DecoSettingsMapping
          (*) Tests in test_deco_settings.py expanded/revised
              accordingly.
          (*) All tests revised/expanded to reflect the above,
              & also to cover things not previously tested
              (e.g. flags args to DecoSettingsMapping.__getitem__;
              that stats.elapsed_secs_logged = sum of elapsed_secs
              column of call history, "to within epsilon";
              call chains and call history; all kinds of methods
              and log_call_settings and call chains)
              New files:
                  record_history.py
                  tests/test_record_history.py
                  docs/record_history.md

0.1.13      - Docs and test_log_calls.py reorganized, mere
              "extra examples" moved to test_log_calls_more.py.
              Tweak to call chain search to make the docs correct
              about treatment of disabled deco'd functions.
0.1.12      - The `file` parameter.
0.1.11      - (All that.)
v0.1.10-b11 - Figured out how to retrieve values of deco'd functions
              on the stack, so now we can & do display call #s
              of deco'd callers when they're enabled and have call
              numbers enabled.
              Used the same technique to implement indentation,
              cf. the 'indent' keyword parameter.

v0.1.10-b10 - Doc log_calls.md done but for Installation & testing
              sections up top... and TOC also up top somewhere.
              197 tests in the runnable doc.
              test_log_calls.py done, slightly more tests than
              the .md so probably 200+.

              Revamped update() method of DecoSettingsMapping:
                * now has a *dicts parameter,
                * skips over immutable settings so user can just
                  pass back a settings dict obtained from e.g. as_dict()

              For benefit of stats.call_history_as_csv, kwargs fields
              are guaranteed have their items sorted by key

v0.1.10-b9 - test_log_calls.py, log_calls.md alllmost done,
             redid stats.total_elapsed - it's available whether or not
             call history is being recorded. Total time spent in
             *logged* calls. For consistency with num_calls_* properties,
             renamed it elapsed_secs_logged

v0.1.10-b8 - Wrote test_proxy_descriptors, simplified proxy_descriptors
             as a result. 100% coverage of proxy_descriptors.py.
             Doctests for get_args_pos in helpers.py, 100% coverage.
             test_deco_settings.py: 100% coverage of deco_settings.py.

v0.1.10-b7 - Reworked __call__ routine to better use inspect module's
             introspection, specifically the bind method. Defaulted
             arg values weren't working quite right.
             Implemented stats.call_history_as_csv, made the fn name
             field in CallRecord the prefixed function name, and added
             a caller_chain field to CallRecord.
             Descriptors on stats object:
                num_calls_total, num_calls_logged, call_history,
                call_history_as_csv, total_elapsed, clear_history (method)
            Need more tests, even more than before.

v0.1.10-b6 - New: stats object available on the deco'd function,
             with attributes num_calls, time_elapsed, call_history.
             Four new keyword parameters:
                log_elapsed, log_call_number, record_history, max_history
             Nice lil class ClassInstanceAttrProxy (stats is one of them).
             All tests from v0.1.10-b5 pass, but we still need more tests,
             and documentation -- now, even more of both than at v0.1.10-b5.

v0.1.10-b5 - Base class for log_calls that does count logging?
             Possible to hide some of the housekeeping obligations?
             call __call__ and bump counters? Arrogate 'enabled' keyword
             shared by all decos, let's say, every one with this base class.
             or _blah_enabled? For now, no.

v0.1.10-b4 - Implement attributes i.e. descriptors on DecoSettingsMapping
             for each setting (e.g. f.log_calls_settings.enabled, you can
             get and set it, i.e. __get__ and __set__ it. Thus,
                    print('d.log_retval =', d.log_retval)
                    d.enabled = 17
                    d.log_retval = False
                    d.log_exit = True
                    d.log_args = 'different_log_args_kwd='
             etc.

v0.1.10-b3 - New feature: mapping interface for settings! Any log_calls-deco'd
             function f now has an attribute .log_calls_settings which behaves
             "just like" a dictionary - __?etitem__, update, __contains__,
             __len__, iteration through names, iteration through .items(),
             a real __repr__ fn, a real __str__ fn.
             Users can get & set the settings of a deco'd function much more
             easily using these interfaces/methods,  no intrusion on deco'd
             function's signature.
             Indirect values still have their place, for controlling an entire
             call subtree/subgraph.
v0.1.10-b2 - Reworked decorator parameter handling: now every parameter except
             prefix can take either direct or indirect values, indirect values
             being names of keyword parameters/arguments of the wrapped function.
             Thus, no more *_kwd parameters (3 fewer). prefix can't be late-bound
             because it's needed immediately, as soon as the wrapped function
             is returned by __call__.
             Updated the doc/tests test_log_calls.py to reflect these changes,
             plus probably other little improvements.

v0.1.10-b1 - Added examples/doctests "Enabling with ints rather than booleans".
             doctests moved to tests/test_log_calls.py. VERSIONS moved to
             CHANGES.txt (this file).
v0.1.9    -- reworked logic of enabled, enabled_kwd parameters:
             enabled_kwd always overrides enabled.
             Fixed: if a wrapped function explicitly declares its enabled_kwd
             parameter, its default value wasn't being used when a caller
             didn't explicitly pass a value for the keyword parameter.
v0.1.8    -- another example: dynamically enabling logging.
v0.1.7    -- actual doc (prose) in the docstrings.
v0.1.6    -- illustrative code converted to doctests;
             metaclass and multi-handler logging examples/tests;
             log_calls is now a package;
             export difference_update.
v0.1.5    -- call chains! + illustrative code; 100% coverage.
v0.1.4    -- switched to dedicated 'keyword' params for specifying enabled,
             logger, and (what prompted the change) args_sep:
             this way the top-level caller can compel logged functions
             lower in the call chain to "conform"; exposed a bug (don't
             use deepcopy [can't deepcopy a logger!] use copy), fixed.
             Added example code at end giving 100% coverage.
v0.1.3    -- logger can be a string naming a keyword arg of wrapped function;
             better output when using a logger.
v0.1.2    -- logger, loglevel keyword parameters
v0.1.1    -- removed redundant function-based decos log_caller, log_args,
             don't want to keep them in sync with the superset log_calls.
