Added hostname and process metadata to enqueued item.
Added hostname, process and time_in_queue metadata to popped queue items.
Added item_preprocessor to QueueDecorator

Allows the adding of arbitrary data to an item's metadata.
Work as normal when popping items that have no metadata.

This is possible if there are jobs in a queue from before bringing
the plugin into a project.
Added util mixin with method to symbolize keys in hashes that might be nested
Sending enqueued, dequeued events from QueueDecorator to event publishers
Removed EventPublisher module/namespace

The references to the various event publishers were needlessly long.