improve readability and styling of map areas' pop-up windows

[critzo]

The current pop-up bubbles show the basic M-Lab data points, but are not formatted for readability. Data points to include in the pop-up:

• Download speeds (median)
• Upload speeds (median)
• Latency - round trip time (mean)

Additionally, if possible, it would be nice to have:

• a description of the census block group area if it exists, at the top of the bubble
• a list of providers in that area
• metrics by provider for that area
• performance by time of day

We should have provider information from piecewise, though it may be incomplete and need to be updated (See: https://github.com/opentechinstitute/piecewise/issues/18), which can be used to list the providers available in a given area (that we know about).

Metrics by provider for a particular shape area and metrics by time of day, either overall (all ISPs) or by ISP, seems like a separate section, perhaps scrolling down in the bubble, or a hidden div that is clicked. Let's investigate whether we have this information already and then add this last bit if we do.

[critzo]

Data by provider is incomplete at best in M-Lab data, so for 8/24 we'll not try to aggregate that data in popups as described above. Instead, we'll add a form element to collect ISP info from users per #41 and #42, and possibly add that data in aggregate to the "city level summary" (see #31) at a later time (after initial launch).

[critzo]

This was addressed in https://github.com/m-lab/bq2geojson/pull/40