Bump readme for 3.3 release.

git-svn-id: https://plugins.svn.wordpress.org/flexible-posts-widget/trunk@894482 b8457f37-d9ea-0310-8a92-e5e31aec5664
Readme updates.

git-svn-id: https://plugins.svn.wordpress.org/flexible-posts-widget/trunk@894504 b8457f37-d9ea-0310-8a92-e5e31aec5664
Readme grammar check!

git-svn-id: https://plugins.svn.wordpress.org/flexible-posts-widget/trunk@894510 b8457f37-d9ea-0310-8a92-e5e31aec5664