chore(package): update prettier to version 1.8.0

Author: greenkeeper[bot]

package.json

@@ -37,7 +37,7 @@
     "eslint-plugin-promise": "^3.5.0",
     "eslint-plugin-standard": "^3.0.1",
     "nyc": "^11.1.0",
-    "prettier": "^1.7.2",
+    "prettier": "^1.8.0",
     "rimraf": "^2.6.1",
     "semantic-release": "^9.0.2",
     "sinon": "^4.0.2"