chore(package): update postcss-simple-vars to version 5.0.0

Author: greenkeeper[bot]

package.json

@@ -48,7 +48,7 @@
     "postcss-import": "^12.0.0",
     "postcss-mixins": "^6.0.1",
     "postcss-scss": "^2.0.0",
-    "postcss-simple-vars": "^4.0.0",
+    "postcss-simple-vars": "^5.0.0",
     "proxyquire": "^2.0.0",
     "rimraf": "^2.6.1",
     "semantic-release": "^15.0.0",