Fix API incompatibility for Google Analytics SDK 3.0.

Google just released it's iOS 3.0 SDK of Google Analytics, which introduced several [API incompatible changes](https://developers.google.com/analytics/devguides/collection/ios/v3/migration). 

As they also removed the download link for legacy SDKs, any current project using CocoaPods to integrate `ARAnalytics/GoogleAnalytics` will fail to build and run. 

Please help review, and let me know if any concerns. Thanks! :smile: