config-sample.json: changed 'user' to 'username'

Author: rdworth

config-sample.json

@@ -3,7 +3,7 @@
 	"pluginsDb": "plugins.db",
 	"wordpress": {
 		"url": "dev.plugins.jquery.com",
-		"user": "admin",
+		"username": "admin",
 		"password": "secret"
 	}
 }