Moved file caching to Minify_Cache_File.

Removed Cache_Lite.
Deprecated UseServerCache() in favor of setCache().
Added Groups controller to ab tests.

lib/Minify/Cache/File.php

@@ -0,0 +1,98 @@
+<?php
+/**
+ * Class Minify_Cache_File  
+ * @package Minify
+ */
+
+class Minify_Cache_File {
+    
+    public function __construct($path = '')
+    {
+        if (! $path) {
+            require_once 'Solar/Dir.php';
+            $path = rtrim(Solar_Dir::tmp(), DIRECTORY_SEPARATOR);
+        }
+        $this->_path = $path;
+    }
+    
+    /**
+     * Write data to cache.
+     *
+     * @param string $id cache id (e.g. a filename)
+     * 
+     * @param string $data
+     * 
+     * @return bool success
+     */
+    public function store($id, $data)
+    {
+        return self::_verifiedWrite($this->_path . '/' . $id, $data);
+    }
+    
+    /**
+     * Get the size of a cache entry
+     *
+     * @param string $id cache id (e.g. a filename)
+     * 
+     * @return int size in bytes
+     */
+    public function getSize($id)
+    {
+        return filesize($this->_path . '/' . $id);
+    }
+    
+    /**
+     * Does a valid cache entry exist?
+     *
+     * @param string $id cache id (e.g. a filename)
+     * 
+     * @param int $srcMtime mtime of the original source file(s)
+     * 
+     * @return bool exists
+     */
+    public function isValid($id, $srcMtime)
+    {
+        $file = $this->_path . '/' . $id;
+        return (file_exists($file) && (filemtime($file) >= $srcMtime));
+    }
+    
+    /**
+     * Send the cached content to output
+     *
+     * @param string $id cache id (e.g. a filename)
+     */
+    public function display($id)
+    {
+        readfile($this->_path . '/' . $id);
+    }
+    
+	/**
+     * Fetch the cached content
+     *
+     * @param string $id cache id (e.g. a filename)
+     * 
+     * @return string
+     */
+    public function fetch($id)
+    {
+        return file_get_contents($this->_path . '/' . $id);
+    }
+    
+    private $_path = null;
+    
+	/**
+     * Write data to file and verify its contents
+     *
+     * @param string $file path
+     * 
+     * @param string $data
+     * 
+     * @return bool success
+     */
+    private static function _verifiedWrite($file, $data)
+    {
+        return (file_put_contents($file, $data, LOCK_EX)
+            && (md5($data) === md5_file($file))
+        );
+    }
+}