Multi syndic

Implementation to allow for a syndic master to connect to multiple masters. This can be done by setting syndic_master's value to a list. What this will do is create a MultiSyndic object which acts similar to MultiMinion-- with a few caveats:
* jobs are returned to the master who originated the request in a best-effort fashion, assuming "master_id" is set in the master config.
* Down masters cause blocking of the syndic process-- this is somewhat avoided using the acceptance_wait_time, but it still blocks
* Events/jobs without a "master_id" in them get sent back to a random master