added redis contrib module

sites/all/modules/contrib/dev/redis/README.PhpRedis.txt

@@ -0,0 +1,37 @@
+PhpRedis cache backend
+======================
+
+This client, for now, is only able to use the PhpRedis extension.
+
+Get PhpRedis
+------------
+
+You can download this library at:
+
+  https://github.com/phpredis/phpredis
+
+Most common Linux distribution should now have packages for this PHP extension
+however if that's not the case for the one you use, use the above link to find
+the release source download links and follow the provided instructions in order
+to compile it for your system.
+
+Default behavior is to connect via tcp://localhost:6379 but you might want to
+connect differently.
+
+Connect via UNIX socket
+-----------------------
+
+Just add this line to your settings.php file:
+
+  $conf['redis_cache_socket'] = '/tmp/redis.sock';
+
+Don't forget to change the path depending on your operating system and Redis
+server configuration.
+
+Connect to a remote host and database
+-------------------------------------
+
+See README.txt file.
+
+For this particular implementation, host settings are overridden by the
+UNIX socket parameter.