rtmp.NewSession hardcodes bandwidth and other parameters

[Alan Noble]

See below. The bandwidth (BW) parameters should be specifiable by the client, based on the intended bit rate, not hard coded to 2500000.

return &Session{
    url:          url,
    inChunkSize:  128,
    outChunkSize: 128,
    clientBW:     2500000,
    clientBW2:    2,
    serverBW:     2500000,
    audioCodecs:  3191.0,
    videoCodecs:  252.0,
            ...

[Alan Noble]

rtmp.Session is now rtmp.Conn but this issue still stands.

[Saxon Milton]

Resolved in PR #412