remove slight delay when displaying callouts
fixes #189: improvements to annotation selection
 * allow selection of enabled annotations even without callout
 * added selection/deselection delegate methods
 * changed `enabled` -> `isEnabled` getter for MapKit consistency
 * simplification of some code
fix shape/circle hit detection passed on presence of fill color
fix problem with containers views & attribution iteration
fixes layer sorting regression introduced in f03045d
Merge branch 'develop' into arc
added ARC branch mention
added ARC notes
fixes #195: added screenshot to README
public/private header cleanup
update ARC podspec
update podspec for development
fix typo
Merge branch 'develop' of github.com:mapbox/mapbox-ios-sdk into develop
refs #197: background/loading image fixes
fixed missing functionality in category
Merge branch 'develop' into arc
bump SMCalloutView but retain old background draw behavior
Merge branch 'develop' into arc
Merge commit upstream 'arc' into 'seatgeek'