Move to "current" event tracking

[notbenh]

this will avoid a flurry of commits for 2013

[igal]

Agreed, the ideal is that the Android app just picks up the new event by querying OCW.

Now that the conference is over, I've begun reworking OCW to provide a complete JSON API and allow fetching things like the current event. Unfortunately, OCW has lots of code that assumes that it's always rendering HTML, so getting it to render JSON-formatted data and error messages and then testing these new workflows is non-trivial.

However, dealing with this is worth doing.

[notbenh]

This is starting to sound like a perfect @pdxhackathon project. Unless we start to have OCW hackathons.