Use literal ^M control characters in gitignore

@wfarr Would like your eyes on this as it's a modification to the GitHub default gitignore file. The diff doesn't show the control characters but https://github.com/fromonesrc/puppet-git/compare#L0L6 is really `Icon^M^M`


Fixes #16

http://blog.bitfluent.com/post/173740409/ignoring-icon-in-gitignore