Refactor Package structure

This commit cleans up the package structure, to make two new top-level
packages `internal` (for internal-use packages) and `pkg` (for general
shared utility code).

internal/hostname/hostname.go

@@ -1,32 +0,0 @@
-// Package hostname provides the hostname.
-package hostname
-
-import (
-	"os"
-
-	"github.com/Showmax/go-fqdn"
-)
-
-// FQDN attempts to return the fully qualified domain name of the host system.
-// If an error occurs, may fall back to the empty string.
-func FQDN() string {
-
-	// try the hostname function
-	{
-		fqdn, err := fqdn.FqdnHostname()
-		if err == nil {
-			return fqdn
-		}
-	}
-
-	// fallback to os hostname
-	{
-		hostname, err := os.Hostname()
-		if err == nil {
-			return hostname
-		}
-	}
-
-	// use the empty string
-	return ""
-}