Need to do:

Done:
- Bug: does not work with custom post types
- Bug: Constructor Error
- Bug: authors cannot "preview" posts in normal way when editing. See: http://wordpress.org/support/topic/simple-preview-not-working
- Bug: scheduled post. See: http://wordpress.org/support/topic/plugin-simple-preview-add-option-for-default-behavior-allow-anonymous-preview
- Check on WP version 3.6