Add support for OpenStreetMap?

[andrewcooke]

See #15.

[andrewcooke]

this seems to be provided by a javascript library called leaflet. there's support for calling that from jupyter but it seems even more complex than the google maps approach (you end up running a node server to run the javascript...).

[andrewcooke]

looking at available libraries, it seems like the kind of thing we could do here is identify what streets were ridden down.