cmd/puppeth: simplifications and pre-built docker images

cmd/puppeth/ssh.go

@@ -116,6 +116,7 @@ func dial(server string, pubkey []byte) (*sshClient, error) {
 	keycheck := func(hostname string, remote net.Addr, key ssh.PublicKey) error {
 		// If no public key is known for SSH, ask the user to confirm
 		if pubkey == nil {
+			fmt.Println()
 			fmt.Printf("The authenticity of host '%s (%s)' can't be established.\n", hostname, remote)
 			fmt.Printf("SSH key fingerprint is %s [MD5]\n", ssh.FingerprintLegacyMD5(key))
 			fmt.Printf("Are you sure you want to continue connecting (yes/no)? ")