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/sebastian/code-unit-reverse-lookup/tests/WizardTest.php

@@ -10,10 +10,12 @@
 
 namespace SebastianBergmann\CodeUnitReverseLookup;
 
+use PHPUnit\Framework\TestCase;
+
 /**
  * @covers SebastianBergmann\CodeUnitReverseLookup\Wizard
  */
-class WizardTest extends \PHPUnit_Framework_TestCase
+class WizardTest extends TestCase
 {
     /**
      * @var Wizard