chore(package): update yarn to version 0.21.3 (#317)

Closes #285

https://greenkeeper.io/

package.json

@@ -149,7 +149,7 @@
     "tslint-jsdoc-rules": "^0.1.2",
     "tuling123-client": "0.0.1",
     "typescript": "2.2.1",
-    "yarn": "0.20.4"
+    "yarn": "0.21.3"
   },
   "files_comment__whitelist_npm_publish": "http://stackoverflow.com/a/8617868/1123955",
   "files": [