new screenshot size is 880x660

git-svn-id: https://plugins.svn.wordpress.org/theme-check/trunk@820024 b8457f37-d9ea-0310-8a92-e5e31aec5664
update lang files

git-svn-id: https://plugins.svn.wordpress.org/theme-check/trunk@820030 b8457f37-d9ea-0310-8a92-e5e31aec5664