new ver 0.7.4 included installation help

git-svn-id: https://plugins.svn.wordpress.org/recent-posts-slider/trunk@814485 b8457f37-d9ea-0310-8a92-e5e31aec5664
tagging update

git-svn-id: https://plugins.svn.wordpress.org/recent-posts-slider/trunk@814487 b8457f37-d9ea-0310-8a92-e5e31aec5664