Merge pull request #1226 from mozilla/greenkeeper/grunt-newer-1.3.0

Update grunt-newer to the latest version 🚀

package.json

@@ -48,7 +48,7 @@
     "grunt-eslint": "19.0.0",
     "grunt-gh-pages": "2.0.0",
     "grunt-mocha-test": "0.13.2",
-    "grunt-newer": "1.2.0",
+    "grunt-newer": "1.3.0",
     "grunt-webpack": "2.0.1",
     "isparta": "4.0.0",
     "json-loader": "0.5.4",