added events onDownload & onListening

just getting the ball rolling
Merge pull request #141 from Sheraff/master

added events onDownload & onListening to get the ball rolling on plugin stuff
better syntax & on-download triggers  even with -q
use proper engine method for on-downloaded event

https://github.com/mafintosh/peerflix/pull/142#issuecomment-61387482
on-downloaded triggers only once
Merge pull request #142 from Sheraff/master

better syntax & on-download triggers  even with -q
0.21.0
Merge upstream 0.21.0

Conflicts:
	app.js
	package.json