use oauth when 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.
being much more efficient about tty
bugfix
Merge pull request #141 from Strider-CD/github-oauth-and-tty

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