add acceptance tests for event tracking

I'm not sure if this is an appropriate direction, might be too nuts-and-bolts for an acceptance test.  However, if you think of our researchers as users (of the data, not the site), then I think it makes more sense.

I'm not thrilled with the usage mongo here, I toyed around with creating an "in memory backend" that would just store the events in a list or something, but figured it was better to get coverage of the entire pipeline.

Reviewers: @rocha, @wedaly