Fairly new to composer, does that message look right?
I don't use Yii so this could well be a dumb question, but is there a reason you didn't use the composer create-project command the instructions say to use?
I'm following this
Ah - I get it. As I said, I don't use Yii so I'm not familiar with its plugins, but honestly I've never seen composer dump 'Killed'. Wish I could help, but I'm afraid I got nothing...
It's ok, I searched via CP and the files were there, I guess it worked
It will affect which files are checked out of a library VCS and added to your project, composer allows you to specify stability.