added filter hooks list link

git-svn-id: https://plugins.svn.wordpress.org/wp-giveaways/trunk@896526 b8457f37-d9ea-0310-8a92-e5e31aec5664
grammar and clarity in readme.txt adjusted

git-svn-id: https://plugins.svn.wordpress.org/wp-giveaways/trunk@896546 b8457f37-d9ea-0310-8a92-e5e31aec5664