Prepare release 1.3.1-beta

https://github.com/FreshRSS/FreshRSS/issues/1113

CHANGELOG.md

@@ -1,6 +1,6 @@
 # Changelog
 
-## 2016-03-xx FreshRSS 1.3.1-beta
+## 2016-03-11 FreshRSS 1.3.1-beta
 
 * Security
 	* Added CSP `Content-Security-Policy: default-src 'self'; child-src *; frame-src *; img-src * data:; media-src *` [#1075](https://github.com/FreshRSS/FreshRSS/issues/1075), [#1114](https://github.com/FreshRSS/FreshRSS/issues/1114)

constants.php

@@ -1,5 +1,5 @@
 <?php
-define('FRESHRSS_VERSION', '1.3.1-dev');
+define('FRESHRSS_VERSION', '1.3.1-beta');
 define('FRESHRSS_WEBSITE', 'http://freshrss.org');
 define('FRESHRSS_WIKI', 'http://doc.freshrss.org');