Added the underscore node_module.

node_modules/underscore/cjs/once.js

@@ -0,0 +1,8 @@
+var partial = require('./partial.js');
+var before = require('./before.js');
+
+// Returns a function that will be executed at most one time, no matter how
+// often you call it. Useful for lazy initialization.
+var once = partial(before, 2);
+
+module.exports = once;