Readme updates in prep for 3.4

git-svn-id: https://plugins.svn.wordpress.org/flexible-posts-widget/trunk@1016179 b8457f37-d9ea-0310-8a92-e5e31aec5664
Version bump for 3.4 release.

git-svn-id: https://plugins.svn.wordpress.org/flexible-posts-widget/trunk@1016181 b8457f37-d9ea-0310-8a92-e5e31aec5664