Implemented CalendarFolder#create_item using a CalendarItem template.
Added function to update attributes of an calendar item.
Handle non duplicable values in CalendarItem template.
Fixed CalendarItem#update_item! when unknown attributes are passed.
CalendarItem template accepts start and end as ISO8601 Strings.
Removed debug code.
Fix CalendarItem template to contain false as value.
Fixed removal of item attributes.
Added Reminder attributes to EWS builder.
Merge branch 'feature-calendar-create-item' of https://github.com/RmMsr/Viewpoint into RmMsr-feature-calendar-create-item

Conflicts:
	lib/ews/types/calendar_folder.rb
	lib/ews/types/calendar_item.rb