Speed up build (#1852)

* single build webpack

* fix demo shell test

ng2-components/config/helpers.js

@@ -0,0 +1,10 @@
+var path = require('path');
+
+var _root = path.resolve(__dirname, '..');
+
+function root(args) {
+  args = Array.prototype.slice.call(arguments, 0);
+  return path.join.apply(path, [_root].concat(args));
+}
+
+exports.root = root;