Show permalink to Tumblr post in WordPress Post listing admin screen.

git-svn-id: https://plugins.svn.wordpress.org/tumblr-crosspostr/trunk@985904 b8457f37-d9ea-0310-8a92-e5e31aec5664
Update changelog in readme, version bump to 0.7.16.

git-svn-id: https://plugins.svn.wordpress.org/tumblr-crosspostr/trunk@985905 b8457f37-d9ea-0310-8a92-e5e31aec5664