Get rid of curl about squeak-ci

[krono]

but why?

[frankshearar]

One less external dependency! If it's in Ruby, Ruby will pull the dependent libraries as necessary.

[krono]

I think tools like curl tend to be much more stable than using Ruby libs for the same thing…

[frankshearar]

Maybe so, but right now it's one more thing that you have to install yourself. With this PR, and #41, and possibly a few more, all you would need to do to is have a Ruby, and run "bundle install" to get a complete dev environment.

Shelling out to curl & tar was great to get things started, but using Ruby makes multiplatform support much easier.