Add option to allow logged in users.
Add help for Logged In Users checkbox.
Whitespace tidy.
Update banner image and screenshots for WordPress 3.8+
Update function documentation.
Remove JavaScript that disables admin RSS checkbox.

No need for this. Users should be able to configure the settings when password protection is disabled.
Restructure admin options display with a "Protected Permissions" group.
Use <label> tabs for options to ensure text is clickable.
Update strings for translation.
Add en_GB translation.