Lots of changes.

Refactoring all RPC/HTTP calls to RPCMessages\
Refactoring WebSocket similar to RPC calls.
Refactoring SlackClient to be a primarily RPC call client.
Adding SlackSocket to handle base socket messaging.
Adding SlackSocketClient to handle all SlackSocket calls and extends
SlackClient so will have both functionality.

The goal is to keep both code separate so we don't end up with a giant
file of calls and variables. SlackSocketClient will be the replacement
for SlackClient from here forward.