When handshake failed, no other `RpcError`.

When timeout occured and disconnected, the state whether handshaked was
performed or not, will be initialiezed also, so instread of raising exception,
just print warning log.
v0.2.1 released
New argument, `stop_reconnect_nth_failed`.

With `stop_reconnect_nth_failed`, client will alive when connection lost
occured. Even if you set `auto_reconnect`, connction will be lost after
retrials.