Version bump to 0.6.0-beta-1.
Add the `include` and `exclude` arguments for the authors widget, which are new arguments for `wp_list_authors()`.
Add the `theme_location` argument to the Nav Menu widget.  This allows users to simply choose the menu they have assigned to a specific location.
Make sure widgets have defaults set so that no undefined index notices pop up when using the_widget(), the theme customizer, or some other method that may come along.