Merge pull request #2156 from mozilla/greenkeeper/raven-js-3.13.1

fix(package): update raven-js to version 3.13.1

package.json

@@ -197,7 +197,7 @@
     "normalizr": "3.2.2",
     "piping": "0.3.2",
     "raven": "1.2.0",
-    "raven-js": "3.12.0",
+    "raven-js": "3.13.1",
     "react": "15.4.2",
     "react-addons-css-transition-group": "15.4.2",
     "react-cookie": "1.0.5",