use relative url, not DOKUBASE which depends on canonical config

Fixes #8
added some video parameters, twitchtv

Fixes #15 related videos by supporting &rel=0
Fixes #25 start at <time> in secondes by &start=35, resp. ends at
&end=45
and &intial_time=35 for twitch.
Also added autoplay=1
Fixes #14 based on patch of @mogoh . Add ?chapter_id=<id> for pointing a
video instead of channel.
Merge pull request #26 from Klap-in/improved

Improved