fix(package): update node-sass to version 4.13.0

Closes #20

Author: greenkeeper[bot]

package.json

@@ -36,7 +36,7 @@
   "pre-commit": "pre-commit",
   "dependencies": {
     "classnames": "^2.2.6",
-    "node-sass": "4.11.0",
+    "node-sass": "4.13.0",
     "prop-types": "^15.6.2",
     "react": "^16.7.0",
     "react-css-modules": "^4.7.4",