Added support for laravel 5.4

removed share() method and replaced with singleton as per laravel 5.4^.

Author: BirdyUK

src/Torann/LaravelMetaTags/MetaTagsServiceProvider.php

@@ -32,7 +32,8 @@ public function boot()
      */
     public function register()
     {
-        $this->app['metatag'] = $this->app->share(function ($app) {
+        // $this->app['metatag'] = $this->app->share(function ($app) { // Removed to support laravel 5.4
+       $this->app->singleton('metatag', function ($app) {
             return new MetaTag(
                 $app['request'],
                 $app['config']['meta-tags'],