Readme updates

git-svn-id: https://plugins.svn.wordpress.org/gif-animation-preview/trunk@928651 b8457f37-d9ea-0310-8a92-e5e31aec5664
Readme updates

git-svn-id: https://plugins.svn.wordpress.org/gif-animation-preview/trunk@928653 b8457f37-d9ea-0310-8a92-e5e31aec5664
Fix readme

git-svn-id: https://plugins.svn.wordpress.org/gif-animation-preview/trunk@928654 b8457f37-d9ea-0310-8a92-e5e31aec5664