fixed readme for proper versioning

git-svn-id: https://plugins.svn.wordpress.org/icestats/trunk@1057211 b8457f37-d9ea-0310-8a92-e5e31aec5664
fixed readme for versioning on wordpress.org

git-svn-id: https://plugins.svn.wordpress.org/icestats/trunk@1057212 b8457f37-d9ea-0310-8a92-e5e31aec5664
updated readme screenshot link to 1.3 folder

git-svn-id: https://plugins.svn.wordpress.org/icestats/trunk@1057213 b8457f37-d9ea-0310-8a92-e5e31aec5664