Use select_related() for the user activity page
Use select_related() for the user activity page

This page was relatively fast, but adding this reduces the number of
queries tremendously.  On my dev machine it went from 102 to 30.
gh-1463 further reduces that to 10.

ReachingOut/unisubs,eloquence/unisubs,ofer43211/unisubs,wevoice/wesub,eloquence/unisubs,ofer43211/unisubs,norayr/unisubs,wevoice/wesub,ReachingOut/unisubs,pculture/unisubs,eloquence/unisubs,wevoice/wesub,ofer43211/unisubs,norayr/unisubs,pculture/unisubs,pculture/unisubs,ofer43211/unisubs,ReachingOut/unisubs,ReachingOut/unisubs,wevoice/wesub,eloquence/unisubs,norayr/unisubs,norayr/unisubs,pculture/unisubs