fix call button

git-svn-id: https://plugins.svn.wordpress.org/sliding-social-icons/trunk@766223 b8457f37-d9ea-0310-8a92-e5e31aec5664
add gplus.png and instagram.png

git-svn-id: https://plugins.svn.wordpress.org/sliding-social-icons/trunk@766225 b8457f37-d9ea-0310-8a92-e5e31aec5664