Switching from unicorn to puma

And mounting sidekiq/web
Modifying validations so that the server works for the current POC
Oops, using `RACK_ENV` instead of `RAILS_ENV` in the Procfile
Using newer hash syntax in config.ru
Making rubocop happy
Revert "Modifying validations so that the server works for the current POC"

This reverts commit fa3a7ace67bff5515d01ddb85cb4c3146ecbf6c4.

Conflicts:
	lib/docker_build_server/app.rb
	lib/docker_build_server/helpers/validation.rb
Restoring `docker-build-worker` in the Procfile
Combining some lines
Making the last test happy
Cleaning up the gem spec a tad
Adding a `^` to the beginning of our regex
Merge pull request #18 from modcloth-labs/switch-to-puma-add-sidekiq-web

Switch to puma add sidekiq web