Fix: Protected var $view error

Running the default install of Slim-Skeleton from composer via the PHP5.4 built in web-server generates the following error:

    Fatal error: Cannot access protected property Slim\Slim::$view in public/index.php on line 17 Call Stack: 0.0004 239656 1. {main}() public/index.php:0 

I don't know slim massively well, but I know the 2.3 upgrade introduced a DI container, and I'm guessing (it is just a guess) it's at this point that `$view` became private (as I never had a problem with the 2.2 skeleton).

Inspecting the source showed that the `view()` method used on line 16 will return the view if nothing is passed to it, so I replaced both calls to `$app->view` in `index.php` with a call to `$app->view()` instead, and this seemed to work as expected!