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/tests/NamespaceUriTest.php

@@ -0,0 +1,29 @@
+<?php declare(strict_types = 1);
+namespace TheSeer\Tokenizer;
+
+use PHPUnit\Framework\TestCase;
+
+/**
+ * @covers \TheSeer\Tokenizer\NamespaceUri
+ */
+class NamespaceUriTest extends TestCase {
+
+    public function testCanBeConstructedWithValidNamespace() {
+        $this->assertInstanceOf(
+            NamespaceUri::class,
+            new NamespaceUri('a:b')
+        );
+    }
+
+    public function testInvalidNamespaceThrowsException() {
+        $this->expectException(NamespaceUriException::class);
+        new NamespaceUri('invalid-no-colon');
+    }
+
+    public function testStringRepresentationCanBeRetrieved() {
+        $this->assertEquals(
+            'a:b',
+            (new NamespaceUri('a:b'))->asString()
+        );
+    }
+}