Owned bin urls

This change means that if you're logged in and you created the first revision, then the url is automatically owned by you (this applies to old bins as well as new bins).

This means if you share the url like http://jsbin.com/abcefg/latest on twitter, anonymous users editing that bin will get their own url, such as http://jsbin.com/zyxwv/1

So, if you've ever shared a url on twitter and wanted to share the latest url, then this will protect the url for unwanted revisions.