Instructions on how to use this (if not obvious from the code and 
help messages there) will be added later.

Note that the line centering used in createModelArcSpectrum.py
needs to be updated to match fixRefModel.py (as of 27 Oct 2016).

For now, could use createModelArcSpectrum.py and then run 
fixRefModel.py on the output (will fix next time a new 
reference model is added).
