update readme file

git-svn-id: https://plugins.svn.wordpress.org/groupdocs-assembly/trunk@802953 b8457f37-d9ea-0310-8a92-e5e31aec5664
updated readme file

git-svn-id: https://plugins.svn.wordpress.org/groupdocs-assembly/trunk@804739 b8457f37-d9ea-0310-8a92-e5e31aec5664