Remove semaphores, copy properties, use .merging, don't includeLibInfo in init

[jaredmixpanel]

The properties object passed to initialize() contains both the lib metadata (i.e. mp_lib and $lib_version) and the user specified super properties: https://github.com/mixpanel/mixpanel-react-native/blob/master/index.js#L67

That object is then passed to the native initialize method as the superProperties param to be registered prior to all event tracking (so there is no need to includeLibInfo when we process the properties: https://github.com/mixpanel/mixpanel-react-native/blob/master/ios/MixpanelReactNative.swift#L25

Additionally, make a copy of the properties dictionary to be passed to setAutomaticProperties. So that it is not the same value that is passed to processProperties and use native .merging() method to create a new dictionary instead of using custom mutating merge function.

Because the lib properties are registered as super properties upon initialization, we do not need to includeLibInfo when we call track or trackWithGroups, only people calls will need them.