update autoloader to consider namespaces for third party libraries: placed and loaded from vendor/namespace/classpath.php

update readability to a newer implementation based on Readability.js (https://github.com/andreskrey/readability.php)
add vendor/Psr/Log interface required for the above

vendor/Psr/Log/InvalidArgumentException.php

@@ -0,0 +1,7 @@
+<?php
+
+namespace Psr\Log;
+
+class InvalidArgumentException extends \InvalidArgumentException
+{
+}