counter model: Rewrite view in d3

Towards #1: "Remove all React and JSX"

May affect #7: "counter model broken on Firefox"

dist/models/counter/counter.js

@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2015-2016, Salesforce.com, Inc.
+ * All rights reserved.
+ * Licensed under the MIT license.
+ * For full license text, see LICENSE.md file in the repo root or
+ * https://opensource.org/licenses/MIT
+ */
+
+'use strict';
+
+let d3 = require('d3');
+let View = function(controller, svg, module) {
+  let model = module.env;
+  svg = d3.select(svg)
+    .classed('counter', true)
+    .append('g');
+  let text = svg.append('text')
+    .attr('x', 10)
+    .attr('y', 20);
+
+  return {
+    name: 'CounterView',
+    update: function(changes) {
+      let output = '';
+      let counterVar = model.vars.get('counter');
+      if (counterVar !== undefined) {
+        output = counterVar.toString();
+      }
+      text.text(output);
+    },
+  };
+}; // View
+
+module.exports = View;

dist/models/counter/package.json

@@ -11,7 +11,7 @@
     "main": {
       "name": "Counter",
       "spec": "counter.model",
-      "view": "counter.jsx"
+      "view": "counter.js"
     }
   }
 }