Render activities.  activities - Array with activities highlight  - True to highlight added activities
function render(activities, highlight) {
    // Top verbs plus 'other'.
    var verbs = topVerbs(activities);

    var selection = d3.select(selector)
      .selectAll("li")
      .data(filterVerbs(activities), function(activity) { return activity.id });
    var li = selection.enter().append("li");

    li.html(function(activity) {
        return activity.html.replace(/(<time.*>).*(<\/time>)/, function(_, head, tail) {
          var date = Date.create(activity.published)
            .format("{Weekday}, {Mon} {d} {h}:{mm} {TT}");
          return head + date + tail;
        })
      });
    li.selectAll("div")
      .append("span").attr("class", "color");
    if (highlight)
      li.attr("class", "highlight").transition()
        .delay(1).attr("class", "");
    selection.exit().remove();
    // Set the color of each activity based on its verb.
    selection.select(".color")
      .style("background-color", function(d) { return verbColor(verbs, d.verb); })
    selection.order();

    renderVerbs(verbs);
  }