Add screenshot and update installation steps.

git-svn-id: https://plugins.svn.wordpress.org/fraudlabs-pro-for-woocommerce/trunk@1024314 b8457f37-d9ea-0310-8a92-e5e31aec5664
rectify readme

git-svn-id: https://plugins.svn.wordpress.org/fraudlabs-pro-for-woocommerce/trunk@1024316 b8457f37-d9ea-0310-8a92-e5e31aec5664