Teams pagination fix

* Fixes failing `GithubApi#find_team` when there are more than 30 teams
* Fetches 100 teams per page
* Iterates through all the pages
* It doesn't look very nice, but that's the suggested solution (https://github.com/octokit/octokit.rb/issues/517)
I'm not sure this assertion is useful. What do you think about simply exercising `add_user_to_repo` here and (per [thoughtbot's style guide](https://github.com/thoughtbot/guides/tree/master/style#testing)) adding a newline between lines 90 and 91?