Updated the readme files.

git-svn-id: https://plugins.svn.wordpress.org/ajax-heartbeat-tool/trunk@923861 b8457f37-d9ea-0310-8a92-e5e31aec5664
Corrected the spelling errors.

git-svn-id: https://plugins.svn.wordpress.org/ajax-heartbeat-tool/trunk@923862 b8457f37-d9ea-0310-8a92-e5e31aec5664