Added test server

Run npm start for demo on localhost

package.json

@@ -10,6 +10,7 @@
   "scripts": {
     "prebuild": "grunt clean:build",
     "build": "grunt build",
+    "start": "npx nodemon utils/server.js",
     "test": "echo \"Error: no test specified\" && exit 1"
   },
   "repository": {
@@ -27,11 +28,13 @@
   },
   "homepage": "https://github.com/kriffe/litegraph.js#readme",
   "devDependencies": {
+    "express": "^4.16.2",
     "google-closure-compiler": "^20171112.0.0",
     "grunt": "^1.0.1",
     "grunt-closure-tools": "^1.0.0",
     "grunt-contrib-clean": "^1.1.0",
     "grunt-contrib-concat": "^1.0.1",
-    "grunt-contrib-copy": "^1.0.0"
+    "grunt-contrib-copy": "^1.0.0",
+    "nodemon": "^1.14.7"
   }
 }