First pass at more advanced 3D OSM buildings, supporting min_height and building relations / parts
First pass at animated loading
Added easing to animated loading
Squashed commit of the following:

commit ea29217a3e10ee98175edba68d3c625a9cddc52d
Author: Robin Hawkes <rob@rawkes.com>
Date:   Tue Jul 1 22:51:54 2014 +0100

    Added DOM container to loading UI

commit 88e0d0289566ceb7bbed4fb2099b42f362a95a21
Author: Robin Hawkes <rob@rawkes.com>
Date:   Tue Jul 1 22:45:31 2014 +0100

    Use a defined DOM element rather than the body
Updated attribution
Fixed default attribution styling