chore(package): update ava to version 0.22.0

Closes #8

Author: greenkeeper[bot]

package.json

@@ -32,7 +32,7 @@
     "postcss": "^6.0.0"
   },
   "devDependencies": {
-    "ava": "^0.19.0",
+    "ava": "^0.22.0",
     "standard": "^10.0.0"
   }
 }