Refactor aggregate helpers and add Dist report

New aggregate report Inbound ACD Call Attempts report with updated README. In
addition, multiple keys in response data were short-circuiting helpers that
build readable hashes of output. New helpers require
ActiveSupport::OrderedHashes to maintain valid associations with response keys,
and ensure that no columns are table rows are left unlabelled. Added this
dependency to gem and made all classes of aggregate reports build the
appropriate style of hash for ::key_translations.