Merge pull request #2004 from mozilla/greenkeeper/sass-loader-6.0.3

Update sass-loader to the latest version 🚀

package.json

@@ -273,7 +273,7 @@
     "redux-devtools": "3.3.2",
     "require-uncached": "1.0.3",
     "rimraf": "2.6.1",
-    "sass-loader": "6.0.2",
+    "sass-loader": "6.0.3",
     "semver": "5.3.0",
     "shelljs": "0.7.5",
     "sinon": "2.1.0",