chore(package): update xo to version 0.30.0

Closes #13

Author: greenkeeper[bot]

package.json

@@ -31,7 +31,7 @@
     "jest": "^22.0.4",
     "lint-staged": "^7.0.0",
     "remove-lockfiles": "^2.0.4",
-    "xo": "^0.20.3"
+    "xo": "^0.30.0"
   },
   "jest": {
     "testEnvironment": "node",