Update stylelint-config-standard (#707)

* Update stylelint-config-standard

When I run 'npm run lint', this warning show up:

Deprecation Warning: 'number-zero-length-no-unit' has been deprecated, and will be removed in '7.0'. Use 'length-zero-no-unit' instead. See: http://stylelint.io/user-guide/rules/length-zero-no-unit/

update package to remove it.

* Update stylelint

to use length-zero-no-unit instead number-zero-length-no-unit.

package.json

@@ -101,8 +101,8 @@
     "react-transform-hmr": "^1.0.4",
     "redbox-react": "^1.2.6",
     "sinon": "^2.0.0-pre",
-    "stylelint": "^6.5.1",
-    "stylelint-config-standard": "^8.0.0",
+    "stylelint": "^6.6.0",
+    "stylelint-config-standard": "^9.0.0",
     "url-loader": "^0.5.7",
     "webpack": "^1.13.1",
     "webpack-hot-middleware": "^2.10.0",