chore(package): update jsdom to version 15.2.1

Closes #3

Author: greenkeeper[bot]

package.json

@@ -4,7 +4,7 @@
   "version": "0.0.2",
   "main": "de-pre.js",
   "devDependencies": {
-    "jsdom": "9.12.0",
+    "jsdom": "15.2.1",
     "jsdom-global": "2.1.1",
     "jslint": "0.10.3",
     "mocha": "3.4.2"