Improve this map

This commit:

- Surfaces the `editlink` option in infoControl to be on by default
- Adds an `open` option to have attribution turned on by default
- Style, "Improve this map" link. Bump up font size and weight and drop to a new line.

References https://github.com/mapbox/www.mapbox.com/issues/3239
#### TODO

- [x] Finalize style
- [x] Fix tests