Allow dependency injected mocks to Manager (barryvdh#245)

By typehinting the Manager class constructor
with concrete implementations, this package will
affect Artisan tests in applications with
Laravel 5.5 auto-discovery enabled.

e.g., EventFake or Mockery partial used during
Artisan integration tests will cause registration
of this package's commands to fail due to
the object not being concrete
Illuminate\Events\Dispatcher.

Instead use inversion of control to dependency
inject by resolving Laravel contracts.

Author: derekmd

src/Manager.php

@@ -1,21 +1,21 @@
 <?php namespace Barryvdh\TranslationManager;
 
+use Illuminate\Contracts\Events\Dispatcher;
+use Illuminate\Contracts\Foundation\Application;
 use Illuminate\Filesystem\Filesystem;
-use Illuminate\Events\Dispatcher;
 use Barryvdh\TranslationManager\Models\Translation;
-use Illuminate\Foundation\Application;
 use Illuminate\Support\Facades\DB;
 use Symfony\Component\Finder\Finder;
 
 class Manager{
 
     const JSON_GROUP = '_json';
 
-    /** @var \Illuminate\Foundation\Application  */
+    /** @var \Illuminate\Contracts\Foundation\Application  */
     protected $app;
     /** @var \Illuminate\Filesystem\Filesystem  */
     protected $files;
-    /** @var \Illuminate\Events\Dispatcher  */
+    /** @var \Illuminate\Contracts\Events\Dispatcher  */
     protected $events;
 
     protected $config;