Updated readme.txt copy

git-svn-id: https://plugins.svn.wordpress.org/wp-conversion-boxes/trunk@963809 b8457f37-d9ea-0310-8a92-e5e31aec5664
Minor changes

git-svn-id: https://plugins.svn.wordpress.org/wp-conversion-boxes/trunk@963810 b8457f37-d9ea-0310-8a92-e5e31aec5664