Namespaces and Resque-based process queue

This release includes two massively breaking changes:

1. Tripod is now namespaced: all of the MongoTripodWhatever classes are now \Tripod\Mongo\Whatever
2. The Mongo based process queue has been replaced with a Resque based queue. There are two jobs/queues that actually do the composite generation. See more about this here: https://github.com/talis/tripod-php/blob/master/docs/operations.md

This introduces another external dependency on Redis for Resque.