chore(package): update prettier to version 2.0.4

Closes #17

Author: greenkeeper[bot]

package.json

@@ -17,7 +17,7 @@
     "babel-preset-env": "^1.6.1",
     "eslint": "^4.11.0",
     "jest": "^21.2.1",
-    "prettier": "^1.8.2"
+    "prettier": "^2.0.4"
   },
   "peerDependencies": {
     "eslint": "^4.11.0",