nits whitespace
use webrtc.io-client directly (symlink was broken)
DataChannel support (with fallback)

This commit adds support for the WebRTC DataChannel API.
If available, it sends all chat messages through DataChannel.
If not, it falls back to using the websocket.
stylefix - removed commas ending hash

Addresses comments in
https://github.com/webRTC/webrtc.io-demo/pull/11#discussion_r2787744
Merge pull request #11 from jbenet/master

DataChannel support