A rake task to hydrate the db with sample data.

Just a little something I need in order to tweak the Sessionizer UX so it does two things I think will be helpful:

1. If you're logged in and you've initially expressed interest, those events will be highlighted.

2. An event attendee can highlight/de-highlight on their device or computer, so over the course of the event, users's won't have to re-find the sessions of interest.