fix(package): update jsdom to version 15.2.1

Closes #188

Author: greenkeeper[bot]

package.json

@@ -33,7 +33,7 @@
     "backbone": "~1.0.0",
     "underscore": "^1.8.3",
     "jquery": "^3.2.1",
-    "jsdom": "^9.1.0",
+    "jsdom": "^15.2.1",
     "request": "^2.2.0"
   },
   "devDependencies": {