Add support for Vimeo Channels

Added support for URLs like:
http://vimeo.com/channels/[channel_name]/[video_id]

I need support for this while using [link_thumbnailer](https://github.com/gottfrois/link_thumbnailer) gem
which in turn uses this one
Line is too long. [83/80]<br>Prefer double-quoted strings unless you need single quotes to avoid extra backslashes for escaping.