add a new setting yoututbe_rel

this is about stopping youtube from showing related (and sometimes inappropriate ;-) content when the video ended.

http://youtu.be/yourvideo?rel=0 did not work any longer. i asked the embedly support for help and they told me to pass `youtube_rel=0` to oembed.

this branch translates rel=0 to youtube_rel=0 for backward compatibility and also adds a new configuration option.

js was minified using http://jscompress.com/

i also did a little css/html cleanup. the empty div got "eaten" by the javascript, so i added the clear to the panel containing the buttons to have them in a separate line.