Add a .gitattributes to ease repository management

Add a .gitattributes to ease repository management

Features:
- enforce LF (Unix) line endings
- omit dev/test resources & code from Git(Hub) archives
- treat minified resources (CSS, JS) as binaries to avoid cluttered diffs

Resources:
- http://git-scm.com/docs/gitattributes
- https://git-scm.com/book/en/v2/Customizing-Git-Git-Attributes
- https://help.github.com/articles/dealing-with-line-endings/
- http://adaptivepatchwork.com/2012/03/01/mind-the-end-of-your-line/
- https://github.com/Danimoth/gitattributes

Signed-off-by: VirtualTam <virtualtam@flibidi.net>