Update readme.

git-svn-id: https://plugins.svn.wordpress.org/fl3r-feelbox/trunk@1018509 b8457f37-d9ea-0310-8a92-e5e31aec5664
Tested on Wordpress 4.0.

git-svn-id: https://plugins.svn.wordpress.org/fl3r-feelbox/trunk@1018510 b8457f37-d9ea-0310-8a92-e5e31aec5664