WIP: removed item and todo

I have the examples working. The tests need to be cleaned up.

I moved the `start_date` to the schedule like it should be.

This is for #3.
Fixed RSpec fo schedule.

Also added ruby-version to keep it consistant right now.

This is for #3. Just need to clean up the code itself now.
Added basic RDoc for all the schedule methods.

This is in help of cleaning up the code. #3
Changed to encode/decode
Removed the Event struct. Using hashes now.
Can now use a block with events_between
dates_between can now take an ad-hoc start date
Properly handling timezones (using DateTime)
Cleaned up naming.

- Changed `next_date` to `next_event_after`
- Removed `todos` from specs. Changed to `events`