Spike public lesson and event site

Based on #9

![CoderDojo - San Francisco](https://f.cloud.github.com/assets/623/412202/5871a0a0-aba6-11e2-9559-49d98498085f.jpg)

- [x] Basic Lesson model.
- [x] Basic Event model.
- [x] Lesson importer.
- [x] Event importer.
- [x] Lessons page.
- [ ] Lesson page with event logic.
- [ ] Basic homepage with upcoming event.
- [ ] Upcoming event newsletter.
- [ ] Notify me of event email.
- [ ] Register for event email.
- [ ] Lesson and Event import rake task.