Test Architecture Tweak

As I was starting to write tests for sync-fork, wanted to try and simplify the test architecture a little bit.
Tests now update the remote with a second repository instead of using local and resetting.
This was just easier for me to think about and more closely mirrors reality.

@kevgo what do you think?

Note: I used git-extract to pull this off my sync-fork branch.
We will always list the right branch in the options once we fix the bug in https://github.com/Originate/git-town/blob/master/features/step_definitions/commit_steps.rb#L14, so I think this can stay as it is.