git kill branchname

@charlierudolph Aaaaahhhh, for some reason some commits meant for this PR ended up in an already merged PR. I was messing around with `git extract` while being distracted on the resource planning call, so that's my (super lame) excuse... Anyways, please take a look at https://github.com/Originate/git-town/commit/738e3e76158a4803c5695abf71349b21d02033f5, and comment there. I will implement the corresponding fixes in this pull request, and once this gets merged its all going to be kind of okay again...  :smile: 
This spec (intentionally) uses open changes that conflict with existing commits. This step checks out different branches. If we don't stash away the conflicting changes, we get false negative test failures here.