MessagesManager should only be accessible via it's shared singleton

Testers can add the verbose init to a category for injecting
dependencies.

// FREEBIE

src/Messages/TSMessagesManager.h

@@ -1,5 +1,6 @@
-//  Created by Frederic Jacobs on 11/11/14.
-//  Copyright (c) 2014 Open Whisper Systems. All rights reserved.
+//
+//  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
+//
 
 #import "TSIncomingMessage.h"
 #import "TSInvalidIdentityKeySendingErrorMessage.h"
@@ -20,14 +21,6 @@ NS_ASSUME_NONNULL_BEGIN
 @interface TSMessagesManager : NSObject
 
 - (instancetype)init NS_UNAVAILABLE;
-
-- (instancetype)initWithNetworkManager:(TSNetworkManager *)networkManager
-                        storageManager:(TSStorageManager *)storageManager
-                    callMessageHandler:(id<OWSCallMessageHandler>)callMessageHandler
-                       contactsManager:(id<ContactsManagerProtocol>)contactsManager
-                       contactsUpdater:(ContactsUpdater *)contactsUpdater
-                         messageSender:(OWSMessageSender *)messageSender NS_DESIGNATED_INITIALIZER;
-
 + (instancetype)sharedManager;
 
 @property (nonatomic, readonly) YapDatabaseConnection *dbConnection;

tests/Messages/TSMessagesManagerTest.m

@@ -1,5 +1,6 @@
-//  Created by Michael Kirk on 9/23/16.
-//  Copyright © 2016 Open Whisper Systems. All rights reserved.
+//
+//  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
+//
 
 #import <XCTest/XCTest.h>
 
@@ -21,6 +22,15 @@ NS_ASSUME_NONNULL_BEGIN
 
 @interface TSMessagesManager (Testing)
 
+// Private init for stubbing dependencies
+
+- (instancetype)initWithNetworkManager:(TSNetworkManager *)networkManager
+                        storageManager:(TSStorageManager *)storageManager
+                    callMessageHandler:(id<OWSCallMessageHandler>)callMessageHandler
+                       contactsManager:(id<ContactsManagerProtocol>)contactsManager
+                       contactsUpdater:(ContactsUpdater *)contactsUpdater
+                         messageSender:(OWSMessageSender *)messageSender;
+
 // private method we are testing
 - (void)handleIncomingEnvelope:(OWSSignalServiceProtosEnvelope *)messageEnvelope
                withSyncMessage:(OWSSignalServiceProtosSyncMessage *)syncMessage;