* upgrade: optimize process of lazy loading for better performance and comfortable experience.
* upgrade: add 'lazyload_slideshow_skip_lazyload' filter, use this you can customize lazy load scope.
* upgrade: add lazy load switch for images, when an image contains 'skip_lazyload' class or attribute, it will no longer be lazy loaded.

git-svn-id: https://plugins.svn.wordpress.org/images-lazyload-and-slideshow/trunk@997336 b8457f37-d9ea-0310-8a92-e5e31aec5664