Added the underscore node_module.

node_modules/underscore/amd/countBy.js

@@ -0,0 +1,12 @@
+define(['./_group', './_has'], function (_group, _has) {
+
+  // Counts instances of an object that group by a certain criterion. Pass
+  // either a string attribute to count by, or a function that returns the
+  // criterion.
+  var countBy = _group(function(result, value, key) {
+    if (_has(result, key)) result[key]++; else result[key] = 1;
+  });
+
+  return countBy;
+
+});