Added .gitignore

Added standard Github .gitignore file

I added the standard .gitignore file from github.  By doing this (especially if you untrack the file files covered by the gitignore (http://stackoverflow.com/questions/3258638/apply-git-gitignore-rules-to-an-existing-repository), there will be fewer files to sync from the repository, since build files and other junk will be omitted.