Gitattributes added (line endings normalized)

It seems different line endings between Mac/Linux/Windows is still making things hard. I've added .gitattributes as described [here](https://help.github.com/articles/dealing-with-line-endings) and normalized files that still had CRLFs.

User's core.autocrlf will still control how files will be copied to working copy, but when writing to index git will convert and CRLFs to LF by itself (for text files).