Improve Landscape Mode

[MosheBerman]

In 5.0.0, auto layout works great for scaling across devices, but we need a better way to handle situations where square calendar cells aren't the most appropriate. Landscape mode, and a custom wrapper view are two such cases.

Right now, using CKCalendarView in landscape mode poses a challenge because of the way the calendar assumes that it's a roughly square-shaped view. Cell are calculated based on the superview's width, and then given a roughly equal height. (The MBCalendarKit 5.0.0 Migration Guide talks about this, too.)

#120 would solve this in a way, because then scrolling (or an alternate week view) is a thing, but it is a lot of work just to get this enhancement as a side benefit. So, this should be considered separately even for the current "classic mode."