allow code completion for andReturnSelf()

[kohlerdominik]

This PR allows code completion for the andReturnSelf()-method by adding the MockInterface as return type.
It uses the same return types as the getMock()-method.

---

For this example, code completion would now the way we'd expect:

$builder->shouldReceive('addThis')
	->andReturnSelf()
	->shouldReceive('addThat')
	->with(13)
	->andReturnSelf()
	->shouldReceive('get')
	->with(23)
	->andReturn($object);

updated to add parameter example

[robertbasic]

Wouldn't you do this with a demeter chain mock?

[kohlerdominik]

Wouldn't you do this with a demeter chain mock?

Thanks for your input!
I stripped my example a little to much. My use case would be with parameters, which isn't supported by the demeter chain:

$builder->shouldReceive('addThis')
	->andReturnSelf()
	->shouldReceive('addThat')
	->with(13)
	->andReturnSelf()
	->shouldReceive('get')
	->with(23)
	->andReturn($object);

[davedevelopment]

Not sure on this one. It works in practice, but only because you usually receive a CompositeExpectation from Mock::shouldReceive. CompositeExpectation has the __call to pass unknown calls back to the mock.