Update dependency prettier to ~2.1.0 (postcss#337)

Co-authored-by: Renovate Bot <bot@renovateapp.com>

Author: renovate[bot]

package.json

@@ -38,7 +38,7 @@
     "eslint-config-problems": "4.0.0",
     "nyc": "^15.0.0",
     "postcss-import": "^12.0.0",
-    "prettier": "~2.0.0",
+    "prettier": "~2.1.0",
     "sugarss": "^2.0.0",
     "uuid": "^8.0.0"
   },