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/phpunit/php-code-coverage/src/Exception/InvalidArgumentException.php

@@ -21,13 +21,13 @@ class InvalidArgumentException extends \InvalidArgumentException implements Exce
      */
     public static function create($argument, $type, $value = null)
     {
-        $stack = debug_backtrace(0);
+        $stack = \debug_backtrace(0);
 
         return new self(
-            sprintf(
+            \sprintf(
                 'Argument #%d%sof %s::%s() must be a %s',
                 $argument,
-                $value !== null ? ' (' . gettype($value) . '#' . $value . ')' : ' (No Value) ',
+                $value !== null ? ' (' . \gettype($value) . '#' . $value . ')' : ' (No Value) ',
                 $stack[1]['class'],
                 $stack[1]['function'],
                 $type