Merge pull request #2070 from mozilla/greenkeeper/karma-webpack-2.0.3

Update karma-webpack to the latest version 🚀

package.json

@@ -262,7 +262,7 @@
     "karma-mocha-reporter": "2.2.2",
     "karma-sinon": "1.0.5",
     "karma-sourcemap-loader": "0.3.7",
-    "karma-webpack": "2.0.2",
+    "karma-webpack": "2.0.3",
     "mocha": "3.2.0",
     "node-sass": "4.5.1",
     "po2json": "0.4.5",