Configure Rubocop

Make Rubocop less strict about arrays in spec/, because
%w doesn't always make for the clearest test data.

The default configuration dislikes inject and recommends
each_with_object, but I disagree.
Add a tabular review aggregator

This aggregates reviews in a suitable format for CSV generation.
Implement a CSV renderer for a user's reviews

This takes the user and a tabular aggregator and combines the
information into a CSV file with keywords translated via the locale
file.
Allow user to download their feedback as CSV

And, by extension, to allow a manager to download a direct report's
feedback as a CSV.
Download all direct reports' reviews as CSV
Remove unused ivar
Distinguish link text for CSV download all vs one
Test all CSV downloading scenarios
Linking to an alternative format is easy

We only need to specify the link parameters we're changing.
Merge pull request #4 from ministryofjustice/csv-exports

CSV exports