remove engine param

lib/core/engine.js

@@ -81,7 +81,7 @@ class Engine {
   }
 
   graphService(_options) {
-    this.registerModule('graph', {engine: this});
+    this.registerModule('graph');
   }
 
   pipelineService(_options) {

lib/modules/graph/index.js

@@ -1,13 +1,10 @@
 const Viz = require('viz.js');
 const fs = require('fs');
 
-// TODO: refactor this class to use the plugin api and not refeneences directly
 class GraphGenerator {
   constructor(embark, options) {
     const self = this;
     this.events = embark.events;
-    // TODO: this is a very bad dependency to have here, needs to be refactored to use events, etc..
-    this.engine = options.engine;
 
     this.events.setCommandHandler("graph:create", function(options, cb) {
       self.generate(options);