Documentation improvement

git-svn-id: https://plugins.svn.wordpress.org/share-on-xing/trunk@993139 b8457f37-d9ea-0310-8a92-e5e31aec5664
Additional docs fixes

git-svn-id: https://plugins.svn.wordpress.org/share-on-xing/trunk@993141 b8457f37-d9ea-0310-8a92-e5e31aec5664