Update ava to the latest version 🚀 (#500)

* chore(package): update ava to version 0.22.0

* chore(package): update lockfile

https://npm.im/greenkeeper-lockfile

package.json

@@ -19,7 +19,7 @@
     "webpack": "2 || 3"
   },
   "devDependencies": {
-    "ava": "^0.21.0",
+    "ava": "^0.22.0",
     "babel-cli": "^6.18.0",
     "babel-core": "^6.0.0",
     "babel-eslint": "^7.1.0",

yarn.lock

@@ -284,9 +284,9 @@ ava-init@^0.2.0:
     read-pkg-up "^2.0.0"
     write-pkg "^2.0.0"
 
-ava@0.21.0:
-  version "0.21.0"
-  resolved "https://registry.yarnpkg.com/ava/-/ava-0.21.0.tgz#cd8d8ea3546f57150dea38548b9f72f8ca583d29"
+ava@0.22.0:
+  version "0.22.0"
+  resolved "https://registry.yarnpkg.com/ava/-/ava-0.22.0.tgz#4c28a1fdef7e749ba0c8131ac18a7ca489eef049"
   dependencies:
     "@ava/babel-preset-stage-4" "^1.1.0"
     "@ava/babel-preset-transform-test-files" "^3.0.0"