use singleton method instead of old share

src/RestableServiceProvider.php

@@ -39,8 +39,7 @@ class RestableServiceProvider extends ServiceProvider
         // Merge config to allow user overwrite.
         $this->mergeConfigFrom($configPath, 'restable');
 
-        $this->app['restable'] = $this->app->share(function ($app)
-        {
+        $this->app->singleton('restable', function ($app) {
             $response = new ResponseFactory($app['view'], $app['redirect']);
 
             $converter = new Format;