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/diff/README.md

@@ -1,16 +1,16 @@
-# Diff
+# sebastian/diff
 
 Diff implementation for PHP, factored out of PHPUnit into a stand-alone component.
 
 ## Installation
 
-To add this package as a local, per-project dependency to your project, simply add a dependency on `sebastian/diff` to your project's `composer.json` file. Here is a minimal example of a `composer.json` file that just defines a dependency on Diff:
+You can add this library as a local, per-project dependency to your project using [Composer](https://getcomposer.org/):
 
-    {
-        "require": {
-            "sebastian/diff": "*"
-        }
-    }
+    composer require sebastian/diff
+
+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/diff
 
 ### Usage