argOfTypeThat() function that allows us to keep HamcrestXXX:: out of our code isn't working

[tpimienta]

The example shown in the README:

Phockito::when($stub)->Foo(argOfTypeThat('B', is(equalTo($b))))->return('Zap');

Does not work. Simply missing return statement. Fixed. Added test case.
Pull request #39. I'm a github noob ;-)