remove phantomjs dependency (#424)

Author: gnikonorov

package.json

@@ -3,8 +3,7 @@
   "dependencies": {
     "grunt": "^1.3.0",
     "grunt-cli": "^1.3.2",
-    "grunt-contrib-qunit": "^4.0.0",
-    "phantomjs-prebuilt": "2.1.15"
+    "grunt-contrib-qunit": "^4.0.0"
   },
   "devDependencies": {
     "sass": "^1.29.0"