Fix jQuery and Tree creation errors (#467)

* Use d3 to handle keyboard event

jQuery isn't always being loaded before the
routing-tree script is executed.

We cannot guarantee when jQuery will be available,
but d3 will be loaded before the routing-tree
script. This change preserves the previous
functionality.

* Add simple case for handling fewer than 3 nodes

The tree algorithm being used doesn't properly handle 1 or 2 nodes.

static/routing-tree.js

@@ -60,8 +60,8 @@ d3.select(".js-find-match").on("click", function() {
   labelServiceHandler();
 });
 
-$(document).on("keyup", function(e) {
-  if (e.keyCode != 13) {
+d3.select(document).on("keyup", function(e) {
+  if (d3.event.keyCode != 13) {
     return;
   }
   labelServiceHandler();
@@ -200,6 +200,15 @@ function update(root) {
 
   var link = svg.selectAll(".link").data(links);
 
+  var drawSimple = nodes.length < 3 ? true : false;
+  if (drawSimple) {
+    // Algorithm fails to assign x attributes if nodes.length < 3. For this
+    // simple case, manually assign values.
+    nodes.forEach(function(n, i) {
+      n.x = i * 180 + 90;
+    });
+  }
+
   link.enter().append("path")
     .attr("class", "link")
     .attr("d", diagonal);