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/exporter/README.md

@@ -162,10 +162,11 @@ LONG_STRING
 
 ## Installation
 
-To add Exporter as a local, per-project dependency to your project, simply add a dependency on `sebastian/exporter` to your project's `composer.json` file. Here is a minimal example of a `composer.json` file that just defines a dependency on Exporter 1.0:
+You can add this library as a local, per-project dependency to your project using [Composer](https://getcomposer.org/):
+
+    composer require sebastian/exporter
+
+If you only need this library during development, for instance to run your project's test suite, then you should add it as a development-time dependency:
+
+    composer require --dev sebastian/exporter
 
-    {
-        "require": {
-            "sebastian/exporter": "1.0.*"
-        }
-    }