Improve plugin description

git-svn-id: https://plugins.svn.wordpress.org/disqus-notify-content-author/trunk@968836 b8457f37-d9ea-0310-8a92-e5e31aec5664
Fix typo on readme

git-svn-id: https://plugins.svn.wordpress.org/disqus-notify-content-author/trunk@968840 b8457f37-d9ea-0310-8a92-e5e31aec5664