Changes Gemfile to https:// source on github instead of git://

Tried to run unit tests, got an error when running bundle install.

This pull request fixes that issue by changing the Gemfile to point to https.

fatal: unable to connect to github.com:
github.com[0: 192.30.252.129]: errno=Connection refused

I can clone other repositories using git:// notation from the same server & I can ssh manually to github.com so I don't know what's going on. If this is indeed some configuration issue on my side please close this pull request.