This should allow us to honor the :plugin directives from project.clj by trampolining.
This is consistent with Leiningen 1.6.x.
It still swallows stuff like 404s, but it's better than hiding everything.
This reverts commit 5b4b8c9. Apparently wget isn't available in production (!)
With curl you can't silence the progress bar without disabling stderr entirely, which is awful. wget lets you tone down the verbosity (not entirely), but doesn't have an overall timeout setting. However, bin/compile is called by Utils.spawn in the slug compiler, which handles timeouts.