Ad campaign tracking

I'd like to get some feedback on this demo.  It's a new replacement for our ad_server demo which was kept in SVN and was pretty out of date.

This one I think is much more relevant to the world of online advertising.  It doesn't try to simulate the entire ad tech ecosystem, just the real-time calculation of the success rates for campaigns.

In a general sense, this is an example of aggregating time-series data by various time frames, which is something that currently requires some data transformation, but eventually can be made more flexible with support for functions in views.