more readme edits

git-svn-id: https://plugins.svn.wordpress.org/mailchimp-for-wp/trunk@988667 b8457f37-d9ea-0310-8a92-e5e31aec5664
Ugh. Add dot.

git-svn-id: https://plugins.svn.wordpress.org/mailchimp-for-wp/trunk@988671 b8457f37-d9ea-0310-8a92-e5e31aec5664