update link to pro demo

git-svn-id: https://plugins.svn.wordpress.org/leaflet-maps-marker/trunk@813309 b8457f37-d9ea-0310-8a92-e5e31aec5664
update styling

git-svn-id: https://plugins.svn.wordpress.org/leaflet-maps-marker/trunk@813311 b8457f37-d9ea-0310-8a92-e5e31aec5664