Watch integration changes and bug fixes

• Watch: Primary change is from communicating with the server via the iOS app to communicating directly from the watch. The interface is now more similar to the iOS/tvOS/app extension interface, though like tvOS and app extension it also only has limited support (notably no A/B testing, codeless tracking, surveys, push notifications - which should come in from the phone and show up on the watch anyway).
  • The old integration method has been removed, though integrating with watch is now basically the same as integrating with the iOS app so it should be easy to change.
  • CocoaPods integration should be on the Mixpanel (default) subspec now for both host and watch instead of Mixpanel/MixpanelHostWatchOS and Mixpanel/WatchOS.
• Fixed an issue that prevented having custom server urls with additional path components. (thanks @gravera!)
• Fixed it so completion block wasn't called twice for errors in decide. #585
• Fixed an issue where disabling the A/B testing gesture wouldn't work if it was disabled too early after initialization. #588
• Updated the docs for distinctId to match the implementation. (thanks @mamaral!) #586
• Fixed a crash during snapshotting a UIView. #583