change stable tag to 3.9.2

git-svn-id: https://plugins.svn.wordpress.org/leaflet-maps-marker/trunk@975443 b8457f37-d9ea-0310-8a92-e5e31aec5664
update demo links to https

git-svn-id: https://plugins.svn.wordpress.org/leaflet-maps-marker/trunk@975444 b8457f37-d9ea-0310-8a92-e5e31aec5664
svn cache?

git-svn-id: https://plugins.svn.wordpress.org/leaflet-maps-marker/trunk@975445 b8457f37-d9ea-0310-8a92-e5e31aec5664