enabling https with fallback

git-svn-id: https://plugins.svn.wordpress.org/ewww-image-optimizer/trunk@956378 b8457f37-d9ea-0310-8a92-e5e31aec5664
updated readme

git-svn-id: https://plugins.svn.wordpress.org/ewww-image-optimizer/trunk@956380 b8457f37-d9ea-0310-8a92-e5e31aec5664