Normalize line endings crlf -> lf

Three files had crlf line endings which showed up as changes after I added the
.gitattributes file that enforces storing line endings as lf.See
https://help.github.com/articles/dealing-with-line-endings
Tabify python tests

I neglected to update my emacs setting to guess tab style and these tests were
committed with indentation in spaces.
Add CONTRIBUTING file