improvement log management

[mattheusv]

I'm suggest to add some package to management the log messages like logrus, and stop to make

if debug {
    fmt.Printf("[DEBUG].......")
}

and add something like this on startup

if verboseFlag {
   logrus.SetLevel(logrus.DebugLevel)
}

and use like this

logrus.Debugf("..........")

[fallion]

Thanks for the issue :) There's a similar one that I was planning to implement. #88