readme tweaks, renamed translation files, and added spanish

git-svn-id: https://plugins.svn.wordpress.org/ewww-image-optimizer/trunk@814733 b8457f37-d9ea-0310-8a92-e5e31aec5664
removing bogus sample-new.jpg

git-svn-id: https://plugins.svn.wordpress.org/ewww-image-optimizer/trunk@814734 b8457f37-d9ea-0310-8a92-e5e31aec5664