Output is not cleared after specify

Hi.

I've a test:

``` php
public function testSomething()
{
$this->specify(
'expect output',
function () {
$this->expectOutputString('lorem ipsum');
(new TestedClass)->doSomething();
}
);
$this->specify(
'expect another output',
function () {
$this->expectOutputString('lorem ipsum');
(new TestedClass)->doSomethingElse();
}
);
}
```

The first specification passes.
Second specification is failing. It expect output to be "lorem ipsum 2", but gots "lorem ipsum 1lorem ipsum 2".

Reproduce the two specify blocks from the issue and inspect how Specify handles PHPUnit output between specifications. Confirm that the second expectation receives only its own output; done means output from the first specification no longer carries into the second.

Written by the indexing model from the issue text.