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/symfony/debug/CHANGELOG.md

@@ -1,6 +1,23 @@
 CHANGELOG
 =========
 
+3.4.0
+-----
+
+* deprecated `ErrorHandler::stackErrors()` and `ErrorHandler::unstackErrors()`
+
+3.3.0
+-----
+
+* deprecated the `ContextErrorException` class: use \ErrorException directly now
+
+3.2.0
+-----
+
+* `FlattenException::getTrace()` now returns additional type descriptions
+  `integer` and `float`.
+
+
 3.0.0
 -----