Improve client socket

[fmcubium]

Mostly fixes banker.get_client_by_socket() to function as intended. The function should return the correct client regardless of what port they are on as long as they are connected and included in the clients list.

The only problem related to this issue is now that an OSError occurs when comparing the two sockets, saying that an operation was attempted on something that is not a socket. This should be false as running type(socket) returns the expected <class: socket.socket>.

Fixes #77

[adamgulde]

I've tried this solution before.. not sure if it works 100%. I said in the TODO message that this wasn't as simple as comparing client.getpeername()[1] with server.getpeername()[1], because I've tried that before. Leaving this PR open until I can sufficiently test it, though. Labeling as question for my own reference later, too.