Simplify user nicename editing on profile/user edit page.

git-svn-id: http://plugins.svn.wordpress.org/edit-author-slug/trunk@828912 b8457f37-d9ea-0310-8a92-e5e31aec5664
Add readme.md for a fancier Github

git-svn-id: http://plugins.svn.wordpress.org/edit-author-slug/trunk@832354 b8457f37-d9ea-0310-8a92-e5e31aec5664