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.
I think the default is that a branch has a tracking branch, unless otherwise specified: https://github.com/Originate/git-town/blob/master/features/step_definitions/branch_steps.rb#L3 If possible, I'd like to keep it that way, but I don't feel strongly about this.