Tweaked:
* state caching logic which will store state only in case if it was changed for 'this' client
* state update request, which won't send partial updates and will send whole cached state
* updated state cahcing logic which allow to clean it up data before sending / storing state

Fixed issues:
* heartbeat interval, when it is set with non-default value after PNConfiguration instance initialization
* copied library into demo projects
* updated library information (debug output in console)
Merge branch 'presence-v3' of github.com:pubnub/objective-c into presence-v3