Add Bookmarkable plugin

As discussed in #217.

I gave this a quick once-over, changed the name from lucidBookmarkable to Bookmarkable, and added a demo. 

Just as a heads-up, I notice that the existing add-ons are pretty consistent about defaulting to {enabled: true}, and this one does not. You'll probably want to change that, and that's fine by me. Up to you!

Thanks again for FooTable. 

 - Amy