Added private_dns and private_ip to output (#4)

Author: s2504s

outputs.tf

@@ -2,7 +2,15 @@ output "public_ip" {
   value = "${aws_eip.default.public_ip}"
 }
 
-output "public_hostname" {
+output "private_ip" {
+  value = "${aws_instance.default.private_ip}"
+}
+
+output "private_dns" {
+  value = "${aws_instance.default.private_dns}"
+}
+
+output "public_dns" {
   value = "${aws_instance.default.public_dns}"
 }