Robin->Hood - enforcing the websocket_transport to be used as a pointer

I prototyped the 'connect' request and it seems that making the `receive_loop` a member of the `websocket_transport` would make it easier to invoke a callback when a message is received. If the mechanism is implemented in the `transport` type we could call it from each transport instead of implementing it in each transport. Because the `receive_loop` schedules itself in a task we need to pass `this` a `shared_ptr` which results in deriving the class from `std::enable_shared_from_this` which results in converting all the usages to `shared_ptr`'s to prevent from incorrect usages resulting in undefined behavior.
Multiple tests have this issue right now, not sure if we want to disable them since we will lose the coverage they provide.