change screenshot.

git-svn-id: https://plugins.svn.wordpress.org/floating-social-buttons/trunk@867901 b8457f37-d9ea-0310-8a92-e5e31aec5664
update class

git-svn-id: https://plugins.svn.wordpress.org/floating-social-buttons/trunk@869263 b8457f37-d9ea-0310-8a92-e5e31aec5664