Add/geojson popups#maps 16

To be used with a geojson layer and the map.
Tells the map how to present each geojson feature based on given configuration

Takes some config for where to find html template and css file, returns an object with a method `present`
that takes a properties object and uses the html template and css to render them.
http://danielhough.co.uk/blog/single-var-pattern-rant/

and also hardest bug i've ever had to find https://github.com/brianleroux/lawnchair/commit/79560cc02eca2f7ec08ab09602f2b1dfcf0d654f