version 1.9 code refactoring + various improvements

git-svn-id: https://plugins.svn.wordpress.org/newsletter-sign-up/trunk@768605 b8457f37-d9ea-0310-8a92-e5e31aec5664
version 1.9 code refactoring + various improvements

git-svn-id: https://plugins.svn.wordpress.org/newsletter-sign-up/trunk@768606 b8457f37-d9ea-0310-8a92-e5e31aec5664
readme fix

git-svn-id: https://plugins.svn.wordpress.org/newsletter-sign-up/trunk@768607 b8457f37-d9ea-0310-8a92-e5e31aec5664