refactoring of checkHtml()

git-svn-id: https://plugins.svn.wordpress.org/wp-fastest-cache/trunk@1051143 b8457f37-d9ea-0310-8a92-e5e31aec5664
0.8.3.5 is live

git-svn-id: https://plugins.svn.wordpress.org/wp-fastest-cache/trunk@1051151 b8457f37-d9ea-0310-8a92-e5e31aec5664