create actual area list for area dropdown

[MilesHeise]

we have a demo dropdown to auto-focus the map on different neighborhoods or towns. based on either client input or just trends in the towns appearing in our data table we should update the set of town names from the 2 demo names to an actual set

[hellonewman]

I'll work on getting centroid points for a list of neighborhoods and municipalities.

[melynnduh]

Feedback from Sarah: We should add a "start typing" text box to enable quick searching of the place list as there are almos 200 places.

Also- this is a good non-technical issue- if someone could clean up the place names with something more recognizable that would be awesome. E.g. "central business district" should be renamed "downtown".

The list is called townConstants.js at https://github.com/CodeForPittsburgh/food-access-map/tree/master/app/components/Map

[MilesHeise]

we should consider updating townConstants.js to a .json I think there is supposed to be a performance difference and the list is long now. do the same to any of our other dropdown constant files that get added just for consistency

[MilesHeise]

PR up currently includes updating the neighbourhood-selection-dropdown to be a typeahead instead of a basic select, so now you can start typing 'mil' and it narrows your options to 'millvale borough'