Merge pull request #300 from rust-lang/greenkeeper-ember-cli-sass-5.3.1

Update ember-cli-sass to version 5.3.1 🚀

Author: alexcrichton

package.json

@@ -35,7 +35,7 @@
     "ember-cli-moment-shim": "1.1.0",
     "ember-cli-qunit": "^1.0.4",
     "ember-cli-release": "0.2.8",
-    "ember-cli-sass": "5.0.1",
+    "ember-cli-sass": "5.3.1",
     "ember-cli-sri": "^1.2.0",
     "ember-cli-uglify": "^1.2.0",
     "ember-data": "2.4.3",