Auto print cred

Automatically download ssh insecure key to print credentials to simplify the steps of S3 configuration https://github.com/hectcastro/docker-riak-cs#amazon-s3
Can you please take a stab at adding support for `wget` if `curl` is not present?

Something like:

```bash
if which curl > /dev/null; then
  curl ...
elif which wget > /dev/null; then
  wget ...
fi
```