Tests fail on windows after git clone with default settings

[peakschris]

The default install of git on Windows clones repos with CRLF line endings. This breaks tests in this repo, which are comparing CRLF files with LF ones created by utilities such as buildifier.

The solution is to check in a .gitattributes file to force clones to retain existing line endings, and to convert CRLF to LF on initial commit.