Better support for hybrid iOS/Mac apps
Better support for hybrid iOS/Mac apps

Currently the code uses ios_app_version to pass version information to
Mixpanel. But if you have an app on both iOS and Mac and want to use the
same Mixpanel project for both this will cause obvious issues. Instead
I've namespaced the mac stuff.

I've also made stats more consistent between the two.

bloom/mixpanel-osx-unofficial