Change version to 2.5

git-svn-id: https://plugins.svn.wordpress.org/ml-slider/trunk@799447 b8457f37-d9ea-0310-8a92-e5e31aec5664
Show resizing gif, only resize new images or when the slideshow size is updated

git-svn-id: https://plugins.svn.wordpress.org/ml-slider/trunk@799448 b8457f37-d9ea-0310-8a92-e5e31aec5664