Add the concept of special events to the app

- Create special events model and migration
- Run migration
- Create special events controller, along with index and show views and modified routes
- Add pry-rails gem for troubleshooting
- Add Marathon 2015 event to seed file
- Remove static events view and events action from static controller
Some events will likely not have a rego page, such as Summer BBQ. Is there a good way to handle that case while still having a rego view? Perhaps a flag on the event that will redirect if a user tries to access the `event/:url_code/rego` path for an event without a rego?