Create a queue maintenance bot

Currently we are totally and utterly unable to affect any real change on the issue queue because we get another 5 issues for every 1 we close. Most of these are garbage issues that should be pointed at the Google Group or Gitter channel, but the cognitive load of having them open is brutal.

To that end (And massive thanks to @laurence-hudson-tessella for the brilliant suggestion), I've started work on a Mary Poppins config for C3, which I'm developing at https://github.com/aendrew/c3-issue-bot. Please feel free to PR.

Will close this issue once the bot is deployed.