Deployment with Capistrano and Puma

- Don’t keep secrets.yml in version control
- Add Capistrano related gems
- Add Puma
- Add a Capfile
- Add a deploy.rb config
- Load Nginx-specific tasks from capistrano-puma
- Generate the default puma + Nginx templates
- Add a deploy/production.rb

	Capistrano requires a file with the stage name to be present in
	config/deploy.

- Generate the puma and Nginx configs on each deployment
- Deployment instructions in the readme