Add pear modules, mail and net_smtp via composer (#93)

Add pear modules, mail and net_smtp via composer, remove php 5.6 build due to phpunit 6

lib/composer/vendor/myclabs/deep-copy/fixtures/f004/UnclonableItem.php

@@ -0,0 +1,13 @@
+<?php
+
+namespace DeepCopy\f004;
+
+use BadMethodCallException;
+
+class UnclonableItem
+{
+    private function __clone()
+    {
+        throw new BadMethodCallException('Unsupported call.');
+    }
+}