More support for different YoutTube URI structures

This PR adds the following features:

- Add support for YouTube "embed" URLs (eg, https://www.youtube.com/v/81Nl7VYFEaI )
- Respect `start` and `end` parameters in YouTube URLs, meaning the video starts and stops at specified points (eg, https://www.youtube.com/v/81Nl7VYFEaI?start=23&end=28 )
- Add URI.js for easier URI processing
(Looking at it again, it appears to be dual-licensed as MIT and GPL, so it actually shouldn't affect the licensing of this project)

Let me know if anything looks out of whack!