Doc Site Generator

Moved in a lot of stuff from esri-leaflet, including the added documentation assembly pipeline. Of course this needs content, but the generation tools are in place, and I swapped out the custom sass stuff for bootstrap just because it's easier and standard.

Clone, npm install, bower install
then
`grunt doc` 
which will generate the docs and start up a server on localhost:8001

Also added the contrib and license md files from Leaflet - need to swap out the names and change urls

Also moved the (minimal) existing js code into the src folder.