Updating plugin version

git-svn-id: http://plugins.svn.wordpress.org/hyper-cache-extended/trunk@1022568 b8457f37-d9ea-0310-8a92-e5e31aec5664
Disabling cleanup process when server is above max load average

git-svn-id: http://plugins.svn.wordpress.org/hyper-cache-extended/trunk@1022602 b8457f37-d9ea-0310-8a92-e5e31aec5664
Fixing wrong saved 'reject' config item
Updating readme
A zero (or less) value means a cached page is valid forever