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/theseer/tokenizer/src/NamespaceUriException.php

@@ -0,0 +1,6 @@
+<?php declare(strict_types = 1);
+namespace TheSeer\Tokenizer;
+
+class NamespaceUriException extends Exception {
+
+}