Reach consensus on WebRTC Signaling Protocol

[albrow]

We have opened a PR in libp2p/specs for a new specification for a WebRTC Signaling Protocol. We need to reach consensus on the spec before we can move forward with browser support for Mesh.

[albrow]

Removing this from the MVP Browser Support milestone. In the near term, we can connect to other browser peers using a relay connection over WebSockets.