Modified peer averages

Adjust averages by the number of questions peers have answered in a particular section/SHELF (eg those who have 0-20% done average this, those with 80-100% done average this). It would give a more accurate set of curves and give a better idea about how well we're actually doing. While it's encouraging when you're one of the 13% to answer the question correctly, that may not be an accurate representation of what we've learned from the answers/explanations.