Made .git at the end of remote optional

It is possible to completely omit adding .git at the end of a remote (i.e. https://github.com/jingweno/gh instead of https://github.com/jingweno/gh.git). gh wasn't accepting this, complaining that the remote doesn't point to a GitHub repository, so I changed some regular expressions in order to allow this. I would be happy to add some tests if you wish.