Get rid of fmt.Print...() methods

[christophd]

Use proper output writer instead and redirect output

[mwmahlberg]

Do you have any preferences in that regard?

My suggestion would be https://github.com/hashicorp/go-hclog or https://github.com/uber-go/zap

However, it could also make sense to define a logger interface and implement it with a logger of choice. This would provide the advantage that the log implementation could easily be swapped, should the need arise.

[mwmahlberg]

@christophd Your thoughts on this?