Convert from Tech to Source Handler

[heff]

The source handler interface has now been merged into core video.js (videojs/video.js#1560) so we could start working toward moving this over towards that interface.

Dependencies:

• Combine the flash tech and HLS tech's currentTime methods #170 Combine the flash tech and HLS tech's currentTime methods
• Remove Buffer Management from Player API Methods #131 Remove Buffer Management from Player API Methods
• Seeking event never fires #175 Seeking event never fires
• Implement a duration method videojs-contrib-media-sources#18 Implement a duration method

After the dependencies are finished, there's pseudo code for HLS in videojs/video.js#1560

[forbesjo]

This is very done