chore(package): update eslint-plugin-unicorn to version 4.0.0

Closes #12

Author: greenkeeper[bot]

package.json

@@ -32,7 +32,7 @@
     "eslint-plugin-node": "5.2.0",
     "eslint-plugin-promise": "3.6.0",
     "eslint-plugin-standard": "3.0.1",
-    "eslint-plugin-unicorn": "2.1.2",
+    "eslint-plugin-unicorn": "4.0.0",
     "istanbul": "0.4.5",
     "last-release-github": "1.1.1",
     "mocha": "4.0.1",