image quality set back to 80

git-svn-id: https://plugins.svn.wordpress.org/wp-performance-pack/trunk@890587 b8457f37-d9ea-0310-8a92-e5e31aec5664
v1.3.1

git-svn-id: https://plugins.svn.wordpress.org/wp-performance-pack/trunk@890588 b8457f37-d9ea-0310-8a92-e5e31aec5664