v1.16.0

• Use the 3.x series of RSpec.
• Use the 0.10.x series of Bitters.
• Improve documentation in generated README for machine setup via bin/setup
  and https://github.com/thoughtbot/laptop script.
• Remove Foreman from Gemfile.
• Use i18n-tasks for missing or unused translations.
• Raise on missing translations in development environment. Fail fast!
• Prevent empty div when there are no flashes.
• Pick random port when generating Rails app so multiple apps can be run via
  Foreman on a development machine at the same time.
• Add normalize-rails gem for resetting browser styles.