Replace blip.tv video links with YouTube counterparts

All the videos once hosted on Blip.tv have sailed away.

- Found what should be their versions hoisted up on YouTube
- Removed default playlist showing as that's gone as well
- Stubbed RailsConf 2008, not uploaded on YouTube account
Merge pull request #1 from randomecho/bliptv-swapout

Replace blip.tv video links with YouTube counterparts