Add area symbols as point clouds by type

[justinlewis]

A point cloud would be a single point for each route placed in a circular cloud colored by type. Andy Woodruff provided an basic example of how he did this:

////  Incomplet. For example only.
var g = symbols.append("g"),
statePath = d3.select( /* selector for the state polygon */ ),
centroid = path.centroid( statePath.datum() );

var total = // whatever the total number of dots is
  dotDiameter = 4,
  dist = 0,
  circumference = 0,
  canFit = 1,
  count = 0,
  angleDelta = 0;
for ( var i=0; i<total; i++ ){
  count++;
  if ( count > canFit ){
    dist += dotDiameter;
    circumference = 2 * dist * Math.PI;
    canFit = Math.floor( circumference / dotDiameter ),
    angleDelta = 2 * Math.PI / canFit;
    count = 0;
  }
  var currentAngle = angleDelta * count;
  var x = Math.cos(currentAngle) * dist,
      y = Math.sin(currentAngle) * dist;

  g.append( "circle" )
    .attr("cx",x+dotDiameter/2)
    .attr("cy",y+dotDiameter/2)
    .attr("r",dotDiameter/2)
    .attr("fill","#ccc")
    .attr("stroke","#666");
}
g.attr("transform","translate(" + centroid.toString() + ")");