Release 0.3.0

• Added event excluding (added single instance, week, month, quarter, or year)
• Added event cancellation (single instance, day, week, month, quarter, or year)
• Added event metadata (single instance, day, week, month, quarter, or year)
• Added Iterators
• Export & import calendar to & from plain objects
• Renamed [add|remove]Schedule[s] to [add|remove]Event[s] in Calendar
• Calendar only keeps track of visible/intersecting schedules
• Change a calendar type & size
• Added Identifiers to describe a span of time using simple numbers