Add thumbnail to widget

git-svn-id: https://plugins.svn.wordpress.org/am-events/trunk@1041346 b8457f37-d9ea-0310-8a92-e5e31aec5664
Update readme version and changelog

git-svn-id: https://plugins.svn.wordpress.org/am-events/trunk@1041347 b8457f37-d9ea-0310-8a92-e5e31aec5664