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: 
I hear you, and agree to some degree. I think there is a continuum of side effects. There are some that we care strongly about, and then the millions of others for which we can't care about, and which are very unlikely anyways. Merely testing the happy path and "assuming no unexpected side effects", waiting for bugs to happen before we care to think about them is the other extreme, and just leads to banana ware (software that is shipped green and ripens later at the clients location). 

So, as a pragmatic compromise, I have removed the checking for commits. I think `git kill` changing commits is unlikely, so I agree we don't need to test for it. `git kill` accidentally killing a branch when it shouldn't is likely, so I'm leaving that in for now. Let's talk more about this in person tomorrow if you feel strongly about taking this out as well.  :)