chore(package): update prettier to version 2.0.4

Closes #19

Author: greenkeeper[bot]

package.json

@@ -33,7 +33,7 @@
     "husky": "^1.1.4",
     "jest": "^23.6.0",
     "lint-staged": "^8.0.4",
-    "prettier": "^1.15.2",
+    "prettier": "^2.0.4",
     "rimraf": "^2.6.2",
     "rollup": "^0.67.1",
     "rollup-plugin-babel": "^4.0.3",