Merge pull request #61 from rhodgkins/master

Added missing semi colon
Added delegate proxy class for forwarding on messages to the original UINavigationControllerDelegate
Uses the navigation controller delegate proxy to allow both the analytics and original delegate to respond to the protocol methods
Added the delegate proxy as a private header file to the pod spec
Merge pull request #62 from rhodgkins/navigation_delegate

Allow original the UINavigationControllerDelegate to still receive messages