Rails 4 upgrade - try 3 (with a brand new clone of the HEAD of versapay/active_sanity repo)

1) Upgraded to rails 4 (now requires a minimum of ruby 1.9.3)
2) Uses 'find_in_batches' to not choke on tables that might have millions of records.
3) Slight performance tweak by not rerunning validations for the 'InvalidRecord' model since it is run in the first step.
4) Added rubocop settings file and fixed all errors reported by it. To rerun this, use the command: 'rubocop -D --autocorrect'
Done - please see latest commit.