Add a block for Mollom Free users to show available remaining legitimate posts

Separating from #423918: Add a basic statistics block (Molstats) → .

Since Mollom is free for up to 100 posts per day, it would be nice to have a block for admins where they can easily monitor how many posts Mollom has processed and how much credit is left. Right now I'm querying the database for the number of posts in the last 24 hrs and displaying the result in a custom block for admins. Needless to say, our number might not be exactly the same as your in-house statistics and we might get into trouble in the 90+ zone.