Release 1.5.4.2, see readme.txt for changelog.

git-svn-id: https://plugins.svn.wordpress.org/wordpress-seo/trunk@949670 b8457f37-d9ea-0310-8a92-e5e31aec5664
Bump to get version number to update on WP.org

git-svn-id: https://plugins.svn.wordpress.org/wordpress-seo/trunk@949675 b8457f37-d9ea-0310-8a92-e5e31aec5664