Move all drivers to PSR autoload, and write tests

cli/Valet/Drivers/KatanaValetDriver.php

@@ -0,0 +1,30 @@
+<?php
+
+namespace Valet\Drivers;
+
+class KatanaValetDriver extends BasicValetDriver
+{
+    /**
+     * Mutate the incoming URI.
+     *
+     * @param  string  $uri
+     * @return string
+     */
+    public function mutateUri($uri)
+    {
+        return rtrim('/public'.$uri, '/');
+    }
+
+    /**
+     * Determine if the driver serves the request.
+     *
+     * @param  string  $sitePath
+     * @param  string  $siteName
+     * @param  string  $uri
+     * @return void
+     */
+    public function serves($sitePath, $siteName, $uri)
+    {
+        return file_exists($sitePath.'/katana');
+    }
+}