Fix the attendance data summary table (was only ever 0% or 100%)
Fix the attendance data summary table (was only ever 0% or 100%)

In 5610380597b86fd7dee14 the attendance views were moved into their own
module, but the line:

  from __future__ import division

... wasn't included so "floor division" was used in calculating the
percentages.  This commit puts the 'from __future__ import division'
back.

mysociety/pombola,mysociety/pombola,mysociety/pombola,mysociety/pombola,mysociety/pombola,mysociety/pombola