Fix race condition in Websocket Retry

This release fixes a bug when attempting to reconnect to a Websocket when one is already open.

Fixes for websockets

This release fixes some issues with websockets that could cause crashes in debug/simulator mode.

Fixes are:

• Ignore stale messages from previous websocket connections in the A/B test designer.
• Fix the retry logic for reconnecting to the designer in debug mode.

Various minor bugfixes

The following neat things have happened:

1. The CHANGELOG file is now up to date with github.
2. The documentation no longer says we have two different identify methods.
3. The internal getTopView method was improved.
4. timeEvent will now set the $duration property as a number and not a string.
5. The $experiments super property is set BEFORE the $experiment_started event is tracked.

Made it possible to copy and build from source

Solved a few issues:

1. XCode 6 stopped creating projects with Prefix.pch files making it impossible to manually build the Mixpanel folder in a new project. We removed our own pch file and imported UIKit as required.
2. Removed calls to MPLog. They were causing spam in production apps, and we should only be using MixpanelDebug and its counterparts.

Some convenience features

We've added the following features to the library:

1. The library will now automatically attempt to connect to the A/B Test designer while in the DEBUG build config. This removes the need for constant option+click silliness but can be turned off using the DISABLE_MIXPANEL_AB_DESIGNER flag.
2. In addition to joinExperiments, there is now a joinExperimentsWithCallback method that will allow developers to run code only after all experiments have been downloaded and applied.

An inapp-notifications test was also updated.

Fix NSCoding serialization failure

Fixes issue #201.

Compatibility with MoPub

Some users reported problems with the 2.6.0 release conflicting with MoPub as both projects have a MPLogging.h. This release changes the name to MPLogger.h to avoid the conflict.

Visual Event Tracking

This release allows our customers to define new elements to be tracked in their app dynamically without having to re-release to the app store.

Default distinct_id for decide queries

Users no longer have to be identified before querying decide.mixpanel.com. This will allow customers to use features like A/B testing without signing up for a People plan.

iOS 8 changes & event timing

This release updates Mixpanel for the SDK changes and deprecations in iOS 8. We have also added the ability to track elapsed time on your events. There are also some bugfixes to optimize the loading of images in A/B tests.