Basho features

@Vagabond and I (@reiddraper) have playing with bors for use at @basho. We've been enjoying it, and wanted to share some of the changes we've made. This isn't a PR per se, it's mostly just to share what we've done, and see if you're interested in bringing any of it upstream. The commit messages should be pretty self-explanatory, but I'll try and highlight some of the changes here:

1. cf5931c7d5448da137ab2b8ca47726525ba8f169:
    Listen for @-mentions for the user bors actually runs as (our name is @borshop).

1. 35afceb35b303d64357ba82182d2b2f03ae2a51b:
    Pass the builbot target_url into the commit status update

1. 98203fe3cf77eda609c3a47eee2eddcbed188ee7:
    Don't close the issue if the auto-merge fails.

1. afbb1bc853a45bfab3efbe39bb75ccebaac3f198:
    Loop through all pull-requests, instead of only operating one-per-run.

1. e1ddf6374199da34b191c330d79e1c467678096c:
    Create unique integration branch per PR. This is so that builbot picks up each commit
    (we have our buildbot set to only run the last commit in a 60-second window).
    Related: 2fcb579ff93d407aea59c7d17a80a2f4897be429.

1. c43a6f66aa07d4a4999e2b452603abd7827b5859
    Add collaborators as reviewers option. This fixes #16.

1. 2eed69bee2b471d62e26b7fd01f26b6794570725
    Allow configurable approval/disapproval tokens (+1, :thumbsup:, etc.).

1. c763fc3a8349e0cfa0215b6f5a1a6647cc3c365c
    Use github's merge message for bors merges.

1. 508928440eb60a3067fc14feaa5bf075072075f9
    Test and merge into target-branch. If the merge-target is not master (master_ref), this commit will
    actually test/merge the correct branch.

1. ce38369bf50f3382449aee72c66348126b8d57b4
    Optionally read the repo name from cmd-line

Lemme know if any of these are interesting. You can simply cherry-pick them if you like, or we'd be happy to open up individual pull-requests for things you like.