Remove Public SRWebSocket Declaration

SocketRocket is a dependency, but not part of the public interface to
Pusher. If you build an app using the OS X framework, you’ll get 
an error saying SRWebSocket cannot be found.
Fix PTPusherMockConnection without SocketRocket

Instead of calling the SocketRocket delegate methods directly, perform 
the socketID and state functions that would normally be performed by 
the SocketRocket delegate manually.
Declare class extension conforming to SRWebSocket

Rather than duplicating functionality.
Merge pull request #157 from codecaffeine/master

Remove Public SRWebSocket.h Import