Added an execute() method to context to catch unhandled commands

examples/catchall.php

@@ -0,0 +1,20 @@
+<?php
+
+require_once __DIR__."/../vendor/autoload.php";
+
+use NoccyLabs\Shell\Shell;
+use NoccyLabs\Shell\Context;
+
+class CatchAllContext extends Context
+{
+    public function execute($cmd, ...$arg)
+    {
+        printf("Executing: %s %s\n", $cmd, join(" ",$arg));
+        return true;
+    }
+}
+
+$myShell = new Shell();
+$myShell->setPrompt("test>");
+$myShell->pushContext(new CatchAllContext());
+$myShell->run();