add hash to URL so users can copy a link taking them to a specific RouteStopPattern

[burritojustice]

like leaflet hash, https://github.com/mlevans/leaflet-hash

but using a routestoppatternID -- think

http://transitland.github.io/route-spotter/r-9q5c-metroexpoline806-87a3a4

this would bring up the map and the nav menu