This exposes the naïveté of the current pitch transform: accuracy ring sizing stays constant, despite vertical screen movement. Still, it looks better pitched than not.
Added some nullability qualifiers in method implementation selectors for consistency with declarations.
The user dot view now has a non-zero size. Previously only its layer was sized properly. Also resolved some pedantic warnings about missing designated initializer overrides.
Xcode 6.3 or above is now required for building this project.
* Cleans up & documents more APIs, especially in location.
* Moves `coordinate` internal and makes use of `location` to retrieve it.
* Moves `title` & `subtitle` internal since part of `MGLAnnotation` protocol.
* Enables `isUpdating` by privately associating weakly with a map view.
