Update dev version for 1.3.1

git-svn-id: https://plugins.svn.wordpress.org/wp-accessibility/trunk@888985 b8457f37-d9ea-0310-8a92-e5e31aec5664
Stable tag to 1.3.1

git-svn-id: https://plugins.svn.wordpress.org/wp-accessibility/trunk@888987 b8457f37-d9ea-0310-8a92-e5e31aec5664