chore(package): update xo to version 0.25.0

Closes #66

Author: greenkeeper[bot]

package.json

@@ -42,6 +42,6 @@
     "coveralls": "^3.0.0",
     "eslint-config-xo-lukechilds": "^1.0.0",
     "nyc": "^11.0.2",
-    "xo": "^0.18.2"
+    "xo": "^0.25.0"
   }
 }