Add cache->set method to engine

Signed-off-by: fzerorubigd <fzerorubigd@gmail.com>

src/Handlebars/Cache.php

@@ -17,7 +17,8 @@
 
 /**
  * Cache interface
- * Base cache interface
+ * Base cache interface, Note that Handlebars.php never call for remove.
+ * Driver should take care of expiered cache.
  *
  * @category  Xamin
  * @package   Handlebars

src/Handlebars/Engine.php

@@ -432,6 +432,7 @@ class Handlebars_Engine
         if ($tree === false) {
             $tokens = $this->getTokenizer()->scan($source);
             $tree = $this->getParser()->parse($tokens);
+            $this->getCache()->set($hash, $tree);
         }
         return $tree;
     }