added LICENSE
Accept environment vars
Don't kill yourself when youtube parsing goes very badly
Use a generic URL from this application for download links

YouTube rotates out links to their videos when links timeout or other
errata make them change. Some podcast managers don't handle this well
and create a duplicate entry; so instead we should serve those from a
consistent URL and forward them to the current location of the video.
On second thought, specify the type of download.

Planning to offer other media types (audio)
That's been bothering me.
Callback hell is such an easy place to visit