Merge pull request #1928 from substars/attempt_retry

extract attempt_retry method in RetryJobs middleware
prep 3.2.4
Merge branch 'master' of github.com:mperham/sidekiq
Update Pro-Changes.md
Lock to Celluloid 0.15.2
extracts worker.perform so call can be enhanced

- defines execute_job as an API hook
Merge pull request #1938 from jejacks0n/extracted_perform

extracts worker.perform so call can be enhanced
Helpful comment is helpful
Czech republic proper shortname
Merge pull request #1948 from Strnadj/czech_country_code

ISO 639-2 Language Czech CODE
added pry-byebug to the sample app
Don't return 404 when no key is provided, redirect to the get request instead.
Merge pull request #1954 from seuros/404

Don't return 404 when no key is provided, redirect to the get request
pubsub change
Merge branch 'master' of github.com:mperham/sidekiq
Update travis to test 2.2.0-preview1
Update web_helpers.rb

fix a bug about zh-cn support.
Merge pull request #1962 from wndfly/master

Update web_helpers.rb
Use warn for printing TTIN, so people don't configure away the ability to debug
Update .travis.yml