chore(package): update yeoman-assert to version 2.2.0

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -36,7 +36,7 @@
     "yeoman-generator": "^0.24.1"
   },
   "devDependencies": {
-    "yeoman-assert": "^2.0.0",
+    "yeoman-assert": "^2.2.0",
     "yeoman-test": "^1.4.0",
     "mocha": "^2.4.5",
     "standard": "^7.1.0"