Cleaning ignored files

Hi,

I added a git command for cleaning ignored files to the source. This is useful if you have files like javascript bundles or a sass cache which is listed in .gitignore. I think cleaning ignored files should be the default behaviour, do you agree? The git clean command used is "git clean -x -f": http://www.kernel.org/pub/software/scm/git/docs/git-clean.html

Best regards,
 Sascha

P.S.: Have you ever thought about turning fast_git_deploy into a gem?