Added release date to change log

docs/Changelog.md

@@ -1,6 +1,6 @@
 ## v3.1.2
 
-Released June ?, 2016
+Released June 12, 2016
 
 - `Improved` Added indexes to SQL fields to improve query execution time (Thanks @qligier, #533)
 - `Improved` Protocol-relative URLs for open graph metadata (#546)