Upgrade: update prettier to version 1.18.0

Author: greenkeeper[bot]

package.json

@@ -50,7 +50,7 @@
     "fbjs": "^1.0.0",
     "jest": "^23.6.0",
     "jsdom": "^15.0.0",
-    "prettier": "^1.17.1",
+    "prettier": "^1.18.0",
     "react": "^16.8.6",
     "react-dom": "^16.8.6",
     "rimraf": "^2.6.3",