Add attr_readers for semester and year
Add schedule method
Add export option to courses command
Add calendar exporter class
Add client export method
Add calendar helpers class
Add calendar dtstart and dtend methods
Add calendar rrule method
Add calendar vevent method
Add calendar export functionality
Add description of --export option
Use format instead of %
Replace reduce with join
Remove schedule variable
Refactor command line options
Rename client.export to client.export_calendar
Use only one instance of schedule class
Ensure file closed
Invert meeting.start_time condition
Pass filename and courses to calendar exporter