Tested up to 4.0

git-svn-id: https://plugins.svn.wordpress.org/steel/trunk@979845 b8457f37-d9ea-0310-8a92-e5e31aec5664
Credentials test

git-svn-id: https://plugins.svn.wordpress.org/steel/trunk@979874 b8457f37-d9ea-0310-8a92-e5e31aec5664
Credentials check

git-svn-id: https://plugins.svn.wordpress.org/steel/trunk@979883 b8457f37-d9ea-0310-8a92-e5e31aec5664
Credentials check

git-svn-id: https://plugins.svn.wordpress.org/steel/trunk@979892 b8457f37-d9ea-0310-8a92-e5e31aec5664
Credentials check

git-svn-id: https://plugins.svn.wordpress.org/steel/trunk@979896 b8457f37-d9ea-0310-8a92-e5e31aec5664