chore(package): update prettier to version 2.0.1

Closes #49

Author: greenkeeper[bot]

package.json

@@ -34,7 +34,7 @@
     "@types/lodash": "^4.14.119",
     "@types/node": "^10.12.14",
     "gh-pages": "^2.0.1",
-    "prettier": "^1.15.3",
+    "prettier": "^2.0.1",
     "tslint-config-prettier": "^1.17.0",
     "typescript": "^3.2.2"
   },