New assertion to test if a given exception is thrown.

Note that this is a minimal implementation, for demonstration purposes, with
just enough code to make it work in PHPUnit.
For a longer discussion see:
http://lars-tesmer.com/blog/2011/08/29/phpunit-better-syntax-for-expecting-exceptions/

Example usage:
$someClass = new SomeClass();
$this->assertThrowsException('InvalidArgumentException', function () use($someClass) {
		$someClass->someMethod();
	}
);

Conflicts:

	Tests/Framework/AssertTest.php