adding tracking-url by sebat

git-svn-id: http://plugins.svn.wordpress.org/tracking-url/trunk@759685 b8457f37-d9ea-0310-8a92-e5e31aec5664
Merge branch 'master' of github.com:sethiele/tracking-url into merge-svn-git

git-svn-id: http://plugins.svn.wordpress.org/tracking-url/trunk@762274 b8457f37-d9ea-0310-8a92-e5e31aec5664
trunk as stable

git-svn-id: http://plugins.svn.wordpress.org/tracking-url/trunk@762275 b8457f37-d9ea-0310-8a92-e5e31aec5664
old readme.txt in new