Merge pull request #2 from zacshenker/master

Added Mixpanel provider, changed logScreen in Flurry & Localytics providers
Updated README and added Zac's name as a contributor
Added AnalyticsKitUnitTestProvider and AnalyticsKitEvent for inspecting
logged events in tests
Renamed AnalyticsKitDebug to AnalyticsKitDebugProvider
Added instance method on unit test provider to clear events
Squelch warning on use of uniqueIdentifier in DEBUG builds
Added error counter event for when errors are logged
Merge pull request #3 from zacshenker/master

New Relic Mobile Monitoring Support
fixed anoying Ok message