fix: use the dust context which is passed in arg

lib/dust-helpers.js

@@ -2,7 +2,7 @@
   if (typeof define === 'function' && define.amd && define.amd.dust === true) {
     define(['dust.core'], factory);
   } else if (typeof exports === 'object') {
-    module.exports = factory(require('dustjs-linkedin'));
+    module.exports = factory;
   } else {
     factory(root.dust);
   }