MAINT: .git is ignored by default by sdist

https://docs.python.org/2/distutils/sourcedist.html
MAINT: Remove build_py

This would only be necessary if we were doing funny things and needed a
custom builder for Python source code.
ENH: Add package_data

Even if the data files are in MANIFEST.in, that doesn't control what gets
installed, only what ends up in the tar.gz. (why? no idea).
Merge pull request #370 from Jorge-C/sdist

Getting setup ready for a release