chore(package): update prettier to version 2.0.4

Closes #61

Author: greenkeeper[bot]

package.json

@@ -37,7 +37,7 @@
     "eslint-plugin-prettier": "^3.1.2",
     "express": "^4.13.4",
     "mocha": "^5.0.0",
-    "prettier": "^1.19.1",
+    "prettier": "^2.0.4",
     "request": "^2.88.0",
     "request-promise": "^4.2.1"
   },