today Button / configurable daysOfTheWeek / chaining

Hi Kyle!

I'm a fan of your calendar and added/changed a few things:

- addEvents method (add events instead of replace them)
- today button & event (jump to current month/year)
- daysOfTheWeek is now part of the options
- chaining for most methods

I would be really happy to see them in the official CLNDR :)