Yamux should not log errors

[jeffreydwalter]

Having Yamux log errors means that software that uses this library have no real control over what messages are logged where. Since Yamux is already returning named errors, which basically contain the message being logged, it would be much nicer if that error could be handled at a higher level and logged there.

[jeffreydwalter]

Nevermind, I didn't see Session had a flag for that.