Consistent creation of ssrc

[davidmoreno]

Ssrc on the source end is important. And needs something repeatable but random. I used a hash on the source name. Which for connections from alsa programs using mido is always the same. But maybe it should be local host name + dest host name hashed. The rfc indicates there's need for collision detection logic. Which I didn't quite grok their example of yet.

See related #34