Revert "Fix callbacks to match the expected number of args"

[deepbrook]

Reverts #39

I just hope this is the last we see of this issue.

[craigjmidwinter]

hmm, I'm seeing this error on 1.0.4--

2018-12-01 18:11:37 ERROR (PysherEventLoop) [websocket] error from callback <bound method Connection._on_open of <Connection(PysherEventLoop, started daemon 139784776562432)>>: _on_open() takes 1 positional argument but 2 were given
2018-12-01 18:11:37 ERROR (PysherEventLoop) [websocket] error from callback <bound method Connection._on_message of <Connection(PysherEventLoop, started daemon 139784776562432)>>: _on_message() takes 2 positional arguments but 3 were given