Add npm-debug task to show package.json contents

This is just the "npm-debug" task from #2, now that the bower parts are no longer relevant.

This is useful to troubleshoot generated package.json contents. I find it helps to spot discrepancies with a plain old package.json that I'm migrating to a lein environment.

I'm open to changing the UI -- it doesn't have to be a task, or called npm-debug. But it would be helpful to add some equivalent behaviour.

Thanks.