Fix some issues with the new design and remove code for the old design

The button was not inserted for users without a youtube account and the code to make
autoplay on playlists work was broken.
Enable size options for playlists

Thanks to the new design we now can easily change the video size for playlist
videos.
Properly calculate available page width

The innerWidth property inludes the scollbars which is why we now use clientWidth.
Fix disabling of spf

The previous approach was not very stable so now we use a method that YouTubeCenter
by YePpHa (https://github.com/YePpHa/YouTubeCenter) introduced.
Remove vimeo support

Vimeo introduced support for html5 in firefox so this is no longer necessary.
Bumb version to 2.1.1