[feature] Matcher for throwException

When passing a closure to $this->spec(), a PHPSpec\Specification\Exception object is created in which you can use PHPSpec DSL

``` php
    function itShouldComplainWhenNotEmptyAndNoNumbersAreGiven() {
        $this->spec(function () {
             $this-calculator("dfsdf")
         })->should->throwException('InvalidArgumentException', 'No numbers given');
    }
```
