Add a panel for text about the currently selected trail

[davemfish]

It should include the trail name, some high-level visitor use summary stats (i.e. total annual visits, total "summer" visits, etc.). This box will be the map "pop-up", triggered by map click and dropdown change, but it will be placed next to the map so it doesn't interfere.

[woodsp]

The box was implemented in Pull #22. In the future we'll use this box to display additional info.