Example using the d3.ringNote
plugin to add circle annotations to a map. Drag the dashed circles and
the text to move the annotation elements. These moveable,
dashed-line circles will disappear if ringNote.draggable(false) is called.
This example also shows how to style (or hide) certain elements of the annotation after it has been drawn. In this example one of the circles is hidden.
The map is a fork of mbostock‘s block: Choropleth