Implement large speed improvements to score calculations. Add page caching to all pages. Small speed improvements to response rate by filtering out
survey items without responses with `none?` `method vs count == 0`.
checkbox change. Draw bar graphs for each academic year selected.
Center bar graphs in their column. Color the columns to match the
sample colors on the checkboxes. Add scores on beta to top of graph.
Automatically display the most recent year of data for the district.
Modify logic for the insufficient data message or the 'measure not based
on student/teacher surveys' message so it only shows if there are no
bars with data to display.
