Merge pull request #40 from tavitar/hotfix/singleton-sp-for-5.4

Switch to using singleton function in service provider

src/Xavrsl/Cas/CasServiceProvider.php

@@ -23,7 +23,7 @@ public function boot()
 	 */
 	public function register()
 	{
-		$this->app['cas'] = $this->app->share(function()
+		$this->app->singleton('cas', function()
 		{
 		    $config = $this->app['config']->get('cas');
 			return new CasManager($config);