added publish date

Author: etsuo

README.md

@@ -14,4 +14,4 @@ You can find the Sakura Api Manual [here](https://github.com/sakuraapi/manual).
 If you find an issue with the develop or master branch API documentation, please open
 a ticket or tack and pull request [here](https://github.com/sakuraapi/core/issues).
 
-Published: {{ page.date }}
+Published: {{ site.time }}