Improve usability on small phones

[graue]

On my 1st gen iPhone SE, the design of the location entry doesn't even have space to fully display one suggestion without scrolling. This screenshot is an older design, but now that the date picker has been added the situation is similar:

(Google Maps side by side for comparison, shows 4)

Also, once you have routes, the map area is pretty small. We might want to customize the location entry to be more compact on small phones, and allow for the bottom drawer to be scrolled down farther.

[graue]

Notes from showing BikeHopper to real people recently:

Limited screen space is still a challenge on some phones. Maybe we could hide the third line of the route params (time bar) until someone taps a clock button further up. Would also help if when you scroll the step by step instructions they replace the top bar.

[graue]

I think the cumulative changes in #91, #140 and #275 fix this adequately.