Adds the geolocation icon and functionality.

Takes the example from
https://www.mapbox.com/mapbox.js/example/v1.0.0/leaflet-locatecontrol/.

Adds the typical arrow icon. If you click or tap it will zoom to current
location and show the location dot.
using cities instead of counties in addresses
moving L.Control.Geolocate
adding Locate dependency in testing requirements
adding control shim to runner.js
fix mock map interaction
Merge pull request #123 from ohnorobo/geolocate

Geolocate