Container::call() supports callable objects:

class Foo {
    public function __invoke() {
    }
}

$container->call(new Foo);

This pull request adds support for providing the class name as string: $container->call('Foo');.

The object will be created using $container->get() before being invoked. For example:

$container->call('Foo');

// is the same as
$container->call(
    $container->get('Foo')
);

This feature adds consistency for Container::call() with #185 and #173. Now Container::call() can call anything and it's awesome.

I have also included tests for the definition dumpers.