Queue classifications

Closes #48 
I'm not a huge fan of model callbacks (read i've been bitten before). They can complicate testing setups (speed / state) and don't scale well under heavy load.  

What do you think about extracting this functionality to a ClassificationQueuing class in the controller? This lends itself to background processing as well so we can get out of the request / response cycle as quickly as possible.

Thoughts?