Changes in version 0.9.1:

* Add thread-safe synchronization primitives.
* Add gruvi.futures.
* Test suite now uses unittest.
* Lots of smaller refactorings to make the API cleaner.
* Remove dependency on six.
* Switch from greenlet to python-fibers.
* Fixed Windows support.

Changes in version 0.9.0:

* Almost complete rewrite.
* First release of beta quality.
