adds pluggable brokers

* added redis broker
 * added django_redis broker
 * added task acknowledgement

django_q/brokers/redis.py

@@ -0,0 +1,43 @@
+import redis
+from django_q.brokers import Broker
+from django_q.conf import Conf, logger
+
+
+class Redis(Broker):
+    def enqueue(self, task):
+        return self.connection.rpush(self.list_key, task)
+
+    def dequeue(self):
+        task = self.connection.blpop(self.list_key, 1)
+        if task:
+            return None, task[1]
+
+    def queue_size(self):
+        return self.connection.llen(self.list_key)
+
+    def delete_queue(self, list_key=None):
+        list_key = list_key if list_key else self.list_key
+        return self.connection.delete(list_key)
+
+    def ping(self):
+        try:
+            return self.connection.ping()
+        except Exception as e:
+            logger.error('Can not connect to Redis server.')
+            raise e
+
+    def set(self, key, value, timeout):
+        self.connection.set(key, value, timeout)
+
+    def get(self, key):
+        if self.connection.exists(key):
+            return self.connection.get(key)
+
+    def get_pattern(self, pattern):
+        keys = self.connection.keys(pattern=pattern)
+        if keys:
+            return self.connection.mget(keys)
+
+    @staticmethod
+    def get_connection():
+        return redis.StrictRedis(**Conf.REDIS)