Adds support for URLs with embedded credentials

I usually use my GitHub username as part of my origin URL, so as to avoid constantly typing it. e.g. ```http://boenrobot@github.com/boenrobot/myRepo.git```.

Sometimes I even consider adding my password (but then I remember I'd be writing it in plain, clearly visible, text...).

This plugin is great, except that it doesn't support this. This pull request adds this ability to the GitHub strategy. Also for BitBucket (though I don't use it).

Note that in order to test this, I had to regenerate the build files... hopefully they don't break your setup.