Added support for extending individual driver classes and driver unit tests

Signed-off-by: dchill42 <dchill42@gmail.com>
diff --git a/system/libraries/Cache/Cache.php b/system/libraries/Cache/Cache.php
index e76fdc5..48bd958 100644
--- a/system/libraries/Cache/Cache.php
+++ b/system/libraries/Cache/Cache.php
@@ -43,12 +43,12 @@
 	 * @var array
 	 */
 	protected $valid_drivers = array(
-		'cache_apc',
-		'cache_dummy',
-		'cache_file',
-		'cache_memcached',
-		'cache_redis',
-		'cache_wincache'
+		'apc',
+		'dummy',
+		'file',
+		'memcached',
+		'redis',
+		'wincache'
 	);
 
 	/**