r10k doesn't pull down dependencies

When I install modules from the forge using puppet module install, it pulls down all the dependent modules as well.

However, when I define a module in r10k, it doesn't.

This can cause issues later when using a module and provider is missing, for example. Also, many modules don't specify their dependencies in the README, so it can be hard to track down what's missing.

It would be nice to have maybe a flag in r10k that tells it to pull down all the dependencies.