Added lodash and AudioBuffer globals to jshint
Add restarting to playbuffer example.
Use send to serve files instead of node-static

node-static doesn't seem to work well with partial file requests. The
'mixer' example uses an <audio> element which will try to partially
load/stream audio, so we can't use node-static.
Add MediaElementNode and MediaStreamSource
Add missing prop checks in beepboop example