Add color-coded routes and extremely basic route and station tooltips to map

[mbjackson-capp]

Resolves #84 . Gets the basics of #89 (which still need to be built out to include route information, ridership data if available, etc.)

Screenshots: As of now, line names display when clicking on a transit line, and station names display when hovering over a station icon (at low enough zoom level, once cluster has fully declustered). Note that even for bus lines typically referred to by a number (as in Chicago's CTA) it displays the text name, not the number, of the route: . The New York colors are wild!! We should look into whether these are substantively meaningful for buses and, if not, consider hard-coding over bus lines to be a more neutral color distinguished from the subway lines: . We're having some display issues with Metra, which is not showing at all. (The other notable commuter rail line in our trial cities, the WES Commuter Rail, is displaying properly without issue on the Portland map.) TODO: Investigate what's going on (hypotheses: extra whitespace in the color strings, column names are slightly different so color column isn't read in)

Also still TODO: figure out how to display overlapping lines side-by-side, which isn't implemented yet.

[lisette-solis]

@mbjackson-capp look great! I wonder if we could lower the opacity of the colors to help with overlapping routes and making it less overwhelming