Implements UserRespository

Add ValidationException.
Add Validator abstract class for form validation.
Add SnippetValidator to validate Snippets.
Add PersistenceServiceProvier to register EloquentSnippetsRepository
implementation.
Move Snippet model to application namespace.
Use Laravel's firstOrCreate()

Use Laravel Eloquent firstOrCreate() instead of own model implementation
for Tags and Votes.
Implement Repositories & move models to namespace

Move Text to Core namespace.
Use ServiceProviders in controllers.
Add validators for Snippets and Comments.
Move login and logout to UsersController, remove
AuthorizationController.
Update database Seeders to use namespaced models.
Update routes.php