[WIP] Merge all Pull Requests in a repo

Closes #75

I wanted to see if this was the right direction for what you had in mind. If so I can finish it up by writing tests.

Let me know!
I'm confused about how that works? Does the client add into the organization as part of the context. Looking here: https://github.com/octokit/octokit.rb/blob/master/lib/octokit/client/pull_requests.rb#L23 it looks like you need an org or owner as part of the method.