Add stream option and command so we don't always have to download a file
Move repeated voice check code to before_invoke hook
Add typing indicators when making YTDLSources
`keep_alive` was not defined until it was created in `received_message`, `ws` is `None` until its actually connected, which doesn't always happen. If an error happens before things start up properly, the client should now clean its objects up (fixes `unclosed client session` warning).
DanielandRapptz
