update readme with new features and a few links

git-svn-id: https://plugins.svn.wordpress.org/wp2yt-uploader/trunk@1019706 b8457f37-d9ea-0310-8a92-e5e31aec5664
fix readme.txt

git-svn-id: https://plugins.svn.wordpress.org/wp2yt-uploader/trunk@1019707 b8457f37-d9ea-0310-8a92-e5e31aec5664