Recover from closed Bunny connection

www.agileplannerapp.com/boards/173808/cards/5649

We initialise Bunny in a rails initialiser. If RabbitMQ
is restarted, the Bunny connection breaks, and the app
throws errors while communicating with RabbitMQ.

Bunny can be instructed to recover from a server-sent
connection.close using `recover_from_connection_close`
option passed to Bunny.new.

This makes it impossible to force client to disconnect,
but it seems unlikely that we'd want to do that.

Bunny docs on Automatic recovery:
http://rubybunny.info/articles/error_handling.html#automatic_recovery
Merge pull request #44 from alphagov/recover-from-connection-close

Recover from closed Bunny connection