Add recurrence to events by way of IceCube::Schedule objects and EventOccurrence objects

This doesn't provide an UI yet.
Add rbenv local version
Clean things up a bit
Cleanup remnants of old event model in view/controller
You can create events with repetition and view them
Tweak views to work a bit better
Oops, leftover git merge stuff
Improve Event#upcoming_dates formatting

In an attempt to make a list of dates more readable, I have removed the month for subsequent dates after displaying it once.

For example, "January 1, 2, 3" instead of "January 1, January 2, January 3."

Better, but doesn't feel right yet.