fix(tooling): Update stylelint

Author: Bernie Zang

package.json

@@ -106,7 +106,7 @@
     "redux-mock-store": "^1.2.1",
     "rimraf": "^2.5.4",
     "style-loader": "^0.13.1",
-    "stylelint": "^7.7.1",
+    "stylelint": "^7.8.0",
     "stylelint-config-standard": "^16.0.0",
     "webpack": "^2.2.0",
     "webpack-dev-server": "^2.2.0"