Build: use different versions of jsdom for Node and iojs testing

Fixes gh-2266

package.json

@@ -42,7 +42,6 @@
     "grunt-jsonlint": "1.0.4",
     "grunt-npmcopy": "0.1.0",
     "gzip-js": "0.3.2",
-    "jsdom": "3.1.2",
     "load-grunt-tasks": "1.0.0",
     "native-promise-only": "0.7.8-a",
     "promises-aplus-tests": "2.1.0",
@@ -54,6 +53,10 @@
     "testswarm": "1.1.0",
     "win-spawn": "2.0.0"
   },
+  "jsdomVersions": {
+    "node": "3.1.2",
+    "iojs": "5.3.0"
+  },
   "scripts": {
     "build": "npm install && grunt",
     "start": "grunt watch",