5.1.4 : major update

git-svn-id: https://plugins.svn.wordpress.org/jm-twitter-cards/trunk@892483 b8457f37-d9ea-0310-8a92-e5e31aec5664
update readme.txt

git-svn-id: https://plugins.svn.wordpress.org/jm-twitter-cards/trunk@892484 b8457f37-d9ea-0310-8a92-e5e31aec5664