Fix issue with existing pullr auth in Github

Github recently changed their app API and we
previously had many pullr entries in the authorized
app list which is now no longer allowed.

[Fix #34]
Update new PR param per GH api docs

Don't need to namespace branch since the repo name
is part of the url

* https://developer.github.com/v3/pulls/#create-a-pull-request
Merge pull request #37 from mojotech/issue/34

Fix issue with existing pullr auth in Github