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/symfony/finder/Exception/ExceptionInterface.php

@@ -13,6 +13,8 @@ namespace Symfony\Component\Finder\Exception;
 
 /**
  * @author Jean-François Simon <contact@jfsimon.fr>
+ *
+ * @deprecated since 3.3, to be removed in 4.0.
  */
 interface ExceptionInterface
 {