Added the underscore node_module.

node_modules/underscore/modules/isFunction.js

@@ -0,0 +1,15 @@
+import tagTester from './_tagTester.js';
+import { root } from './_setup.js';
+
+var isFunction = tagTester('Function');
+
+// Optimize `isFunction` if appropriate. Work around some `typeof` bugs in old
+// v8, IE 11 (#1621), Safari 8 (#1929), and PhantomJS (#2236).
+var nodelist = root.document && root.document.childNodes;
+if (typeof /./ != 'function' && typeof Int8Array != 'object' && typeof nodelist != 'function') {
+  isFunction = function(obj) {
+    return typeof obj == 'function' || false;
+  };
+}
+
+export default isFunction;