Simplify version naming

[mattgreene]

The makefile currently uses separate variables for VERSION and RELEASE (sourced from files), and uses one or both inconsistently to generate artifacts. Consolidate these into a single VERSION file to simplify naming convention and minimize the potential for errors when creating a release via github.

[swormke]

Make sure that when you do this you also deal with the versioning in the docs/config.py file. If you use the version file in its current form you are probably going to have to read the file in and set a variable VERSION= and use that to populate the version and release in the config file.

See PR #34 for more info...