Update web map in Map Tools example

[oevans]

The web map in the Map Tools example should be updated with a map that better highlights the app and web mapping best practices. The first item is a major issue; the others are minor.

• Major issue -- The Boston Marathon layer has random "null" polygons that should be removed and labels that conflict with the basemap (remove labels or change basemap).
• The layer also should be symbolized using one of the numeric attributes and it's name changed to something like "Boston Marathon Registrations."
• A second layer should be added to the map so that users can better see how the layer toggle tool works.
• The published layer should have field aliases. The table shows database-style field names with underscores and abbreviations.

[jgravois]

it'd be pretty trivial to swap in an entirely different webmap. can you suggest an alternate?

i'd also recommend including a [View it live]() link in the README.

[kellyhutchins]

@oevans thanks we'll fix the map today.