Modified custom.css

git-svn-id: https://plugins.svn.wordpress.org/x-scroll-to-top-responsive/trunk@949562 b8457f37-d9ea-0310-8a92-e5e31aec5664
Add setting menu and WordPress default color picker

git-svn-id: https://plugins.svn.wordpress.org/x-scroll-to-top-responsive/trunk@949563 b8457f37-d9ea-0310-8a92-e5e31aec5664
Add color picker active hook

git-svn-id: https://plugins.svn.wordpress.org/x-scroll-to-top-responsive/trunk@949564 b8457f37-d9ea-0310-8a92-e5e31aec5664