use github oauth when there's no privkey + tty improvements

Now for the github "kickoff" screen we don't show them two options; we always
go with "no_ssh", which will cause strider-simple-worker to fallback to using
the api key.

We also have much better tty support, so things like git clone won't take up
1000 lines. I love it. It's really like you're watching a terminal real time.

http://youtu.be/8uERxPFw5Ck