Allow scoped names for project names

[nyrosmith]

Currently it is not possible to create a CLI with npm scope like '@myorg/my-cli'. I am suggesting using https://www.npmjs.com/package/validate-npm-package-name as it gives meaningfull error messages out of the box.

@jamonholmgren I'd be happy to provide a PR if you want me to fix this.

PS: Thank you for gluegun. It's just fantastic!

[jamonholmgren]

@nyrosmith I think your idea is great. I'd love a PR!