Update: json_last_error required PHP 5.3

git-svn-id: https://plugins.svn.wordpress.org/wp-to-twitter/trunk@871541 b8457f37-d9ea-0310-8a92-e5e31aec5664
Switch stable tag to 2.8.5

git-svn-id: https://plugins.svn.wordpress.org/wp-to-twitter/trunk@871543 b8457f37-d9ea-0310-8a92-e5e31aec5664