Changed redis mechanism to pub/sub poll.

I need feedback on this, I am concerned that a blocking condition could
occur with the polling and potential failure to exit the loop in a
graceful state.
Updated to ensure composer is updated to the latest version.
Revert "Changed redis mechanism to pub/sub poll."

This reverts commit eaa07725da34ff00aa316368c10c9969bf013339.
Revert "Updated to ensure composer is updated to the latest version."

This reverts commit 338bb21d16b7b1fecd27e6d93e355381cdfce888.
Removed the sudo from the celery worker init

This accomodates the latest version not allowing celery to run with
priveleges.
Commiting and vaulting.

Since celery has a commited roadmap that only includes AMQP and Redis
backends, Rhubarb will only actively support those features in the
roadmap.
Begining of 3.1 branch

Branches will now follow as close as possible to the celery version
lines.
Working to bring up to Celery 3.1 API happiness

- Moved phpunit.ini => phpunit.ini.dist
- Fixed PHPAmqp Connector to make virtual host config behaviour uniform
  with celery as `zircote/amqp`
- Dropping support for MongoDB backend keeping inline with Celery
  roadmap see: http://docs.celeryproject.org/en/latest/whatsnew-3.1.html#preface
- updated `.travis.yml` for test execution to drop mongo support
- updated composer.json: removed "suggests" ext-mongo