add newline to printf
Merge pull request #457 from koenpunt/patch-1

Add newline to printf command
Using an `nvm_curl` function instead of `curl`/`wget` directly.
Use `nvm_curl` instead of `curl` directly, which has a `wget` fallback.
Add some more curl → wget argument munging
Make `nvm_curl` do a runtime check if `curl` is available.
Make sure both wget and curl work.