api: Implement bucket notification. (#2271)

* Implement basic S3 notifications through queues

Supports multiple queues and three basic queue types:

1. NilQueue -- messages don't get sent anywhere
2. LogQueue -- messages get logged
3. AmqpQueue -- messages are sent to an AMQP queue

* api: Implement bucket notification.

Supports two different queue types

- AMQP
- ElasticSearch.

* Add support for redis

vendor/gopkg.in/olivere/elastic.v3/query.go

@@ -0,0 +1,13 @@
+// Copyright 2012-2015 Oliver Eilhard. All rights reserved.
+// Use of this source code is governed by a MIT-license.
+// See http://olivere.mit-license.org/license.txt for details.
+
+package elastic
+
+// Query represents the generic query interface. A query's sole purpose
+// is to return the source of the query as a JSON-serializable object.
+// Returning map[string]interface{} is the norm for queries.
+type Query interface {
+	// Source returns the JSON-serializable query request.
+	Source() (interface{}, error)
+}