"Popular content" includes nodes user does not have access to

Issue Summary

Hi

This module has an option to send a block of popular content along with the message. A brilliant feature as it aids in marketing the site.

However, currently the content linked to may not be visible to anonymous/less priviledged users. (I think it uses the same access permissions as those of the forward email sender.)

This is sort of a deal breaker as people are sent links they cannot click on.

I think what the best (Read: "easiest" because "best" can also be defined by other measures) fix would be to send links that are viewable by Anonymous users.