Added wikipedia support

Requires the thumbnail fix and a change to how hostname is determined.
The hostname change is required to support *.wikipedia.org and other sites
with multiple possible starts to the domain name. It splits at peiods,
then throws away all but the last two items before recombining, ie.

en.wikipedia.org -> 'en','wikipedia','org' -> 'wikipedia','org',
wikipedia.org

www.imgur.com -> 'www','imgur','com' -> 'imgur','com', -> imgur.com

Breaks on multiple .domains like .co.uk though. A better solution may be
needed.

Finally, I found where the modules need to be listed in chrome's manifest,
but I haven't tested this with any of the other browsers.
Merge pull request #16 from amoliski/module-wikipedia

Added wikipedia support