120 add bundle audit gem to bin quality

Related to: https://github.com/fs/rails-base/issues/120

- Add bundler-audit gem for determining unpatched versions of gems
- Upgrade unpatched activesupport 4.0.4 upto 4.0.5
- Fix rubocop worning in spec/factories/users.rb
@juggler what about in both: development and test groups? Because it should run in Semaphore too.