Extract license to its own file
Don't call deprecated methods in specs
Clean up and fix some spec errors via testing in 1.8
Silence bundler warning in ruby-2.0.0 (all green!)
Add Occurrence class to handle end_time

Schedule occurrences are wrapped in a Time-like object that wraps the
start & end time into a single concept. All methods delegate to the
occurrence's enclosed start_time so it continues to behave like before.

Fixes #119