Update nokogiri gem to 1.6.4.1
Update rubocop gem to 0.27.0
Update turbolinks gem to 2.5.2
Update mysql2 gem to 0.3.17
Add sidekiq gem
Update sidekiq gem to 3.2.6
Update rubygems version to 2.4.3
Add devise-async gem
Configure devise-async for using sidekiq
Add lograge gem
Enable lograge. Rails logs squasher for production env.
Update ruby to 2.1.5
Update bundler to 1.7.6