readme https to http link fixed

git-svn-id: https://plugins.svn.wordpress.org/rss-post-importer/trunk@1008374 b8457f37-d9ea-0310-8a92-e5e31aec5664
readme https to http link fixed

git-svn-id: https://plugins.svn.wordpress.org/rss-post-importer/trunk@1008375 b8457f37-d9ea-0310-8a92-e5e31aec5664