screenshots added and readme.txt change

git-svn-id: https://plugins.svn.wordpress.org/woosocio/trunk@871917 b8457f37-d9ea-0310-8a92-e5e31aec5664
screenshot names added in readme.txt

git-svn-id: https://plugins.svn.wordpress.org/woosocio/trunk@871918 b8457f37-d9ea-0310-8a92-e5e31aec5664