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/pear/net_socket/phpunit.xml.dist

@@ -0,0 +1,29 @@
+<phpunit bootstrap="vendor/autoload.php"
+         cacheTokens="false"
+         colors="true"
+         convertErrorsToExceptions="true"
+         convertNoticesToExceptions="true"
+         convertWarningsToExceptions="true"
+         stopOnError="false"
+         stopOnFailure="false"
+         stopOnIncomplete="false"
+         stopOnSkipped="false">
+
+    <testsuites>
+        <testsuite name="Test Suite">
+            <directory suffix=".php">tests/</directory>
+        </testsuite>
+    </testsuites>
+
+    <filter>
+        <whitelist>
+            <directory suffix=".php">Net/</directory>
+        </whitelist>
+    </filter>
+
+    <logging>
+        <log type="coverage-clover" target="build/logs/clover.xml"/>
+        <log type="coverage-html" target="build/coverage/"/>
+    </logging>
+
+</phpunit>