Upgrade Sidekiq from 4.1.2 to 4.1.4.
Adds a dependency on Sinatra and allows Sinatra 2 for eventual support of Rack 2.
Changelog: https://github.com/mperham/sidekiq/blob/master/Changes.md#414
Working toward #14286 (moved).
cc: @rspeicher 
Adds a dependency on Sinatra and allows Sinatra 2 for eventual support of Rack 2.
Changelog: https://github.com/mperham/sidekiq/blob/master/Changes.md#414
Working toward #14286 (moved).
cc: @rspeicher