BkPHcgQL3V

Allow signing mutable data asynchronously

1

This can be useful if we want to keep the private key out of the process. **What is the purpose of this pull request? (put an "X" next to item)**...

RTCPeerConnection.createOffer only implements the old non-Promise API

2

In the context of webtorrent-hybrid, I'm seeing stack traces such as the following: ``` /myapp/node_modules/electron-webrtc/src/RTCPeerConnection.js:189 cb(offer) ^ TypeError: cb is not a function at /myapp/node_modules/electron-webrtc/src/RTCPeerConnection.js:189:11 at Daemon. (/myapp/node_modules/electron-webrtc/src/RTCPeerConnection.js:277:11) at Object.onceWrapper...