Add Rubocop

- Pull in the 37signals house style
- Autofix violations
- Add to CI

lib/kamal/commands/app.rb

@@ -15,7 +15,7 @@ class Kamal::Commands::App < Kamal::Commands::Base
       "--detach",
       "--restart unless-stopped",
       "--name", container_name,
-      *(["--hostname", hostname] if hostname),
+      *([ "--hostname", hostname ] if hostname),
       "-e", "KAMAL_CONTAINER_NAME=\"#{container_name}\"",
       "-e", "KAMAL_VERSION=\"#{config.version}\"",
       *role.env_args,