Create .gitattributes

Contributors:

GitHub online editor
  No further action needs to be taken. Hopefully it will recognize
  .gitattributes and not mess up the line endings.

Git or GitHub for Windows
  Windows
    Please execute `git config --global core.autocrlf true` in a
    command prompt.
  Linux, BSD, OS X
    Please execute `git config --global core.autocrlf input` in a
    terminal.