added flush method to redis cache interface

redis_cache/cache.py

@@ -85,6 +85,9 @@ class CacheClass(BaseCache):
         key = self._prepare_key(key)
         self._cache.delete(key)
         
+    def flush(self, all_dbs=False):
+        self._cache.flush(all_dbs)
+
     def get_many(self, keys):
         "Retrieve many keys."
         return self._cache.mget(map(self._prepare_key, keys))