Updates bunny to 1.4.x

Following from the refactor, this gets us up to Bunny 1.4.x.  The newer versions have automatic recovery, so a next step following this release is to consider removing all of our custom recovery handling code and rely on Bunny's recovery handling code.  It will undoubtedly be better since there are many tests to ensure it works correctly.  Anyway, if we're happy with this, we can put this on staging for Core, CA, Pusher, etc and let it run for a little while.