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/github.com/streadway/amqp/auth.go

@@ -0,0 +1,44 @@
+// Copyright (c) 2012, Sean Treadway, SoundCloud Ltd.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+// Source code and contact info at http://github.com/streadway/amqp
+
+package amqp
+
+import (
+	"fmt"
+)
+
+// Authentication interface provides a means for different SASL authentication
+// mechanisms to be used during connection tuning.
+type Authentication interface {
+	Mechanism() string
+	Response() string
+}
+
+// PlainAuth is a similar to Basic Auth in HTTP.
+type PlainAuth struct {
+	Username string
+	Password string
+}
+
+func (me *PlainAuth) Mechanism() string {
+	return "PLAIN"
+}
+
+func (me *PlainAuth) Response() string {
+	return fmt.Sprintf("\000%s\000%s", me.Username, me.Password)
+}
+
+// Finds the first mechanism preferred by the client that the server supports.
+func pickSASLMechanism(client []Authentication, serverMechanisms []string) (auth Authentication, ok bool) {
+	for _, auth = range client {
+		for _, mech := range serverMechanisms {
+			if auth.Mechanism() == mech {
+				return auth, true
+			}
+		}
+	}
+
+	return
+}