chore(package): update ava to version 0.22.0

Author: greenkeeper[bot]

package.json

@@ -35,7 +35,7 @@
     "rucksack-css": "^0.9.1"
   },
   "devDependencies": {
-    "ava": "^0.21.0",
+    "ava": "^0.22.0",
     "coveralls": "^2.13.1",
     "nyc": "^11.0.3",
     "rewire": "^2.5.2",