'UnexpectedValueException' occurs when using hierarchical namespace

* /path/to/project/codeception.yml

```
include:
  - src/Foo/Bar
paths:
  log: tests/logs
```

* /path/to/project/src/Foo/Bar/codeception.yml

```
namespace: Foo\Bar
```

Then, i run a test 'codecept run', it fails:

```
[UnexpectedValueException]
The stream or file "/path/to/project/tests/logs/Foo/Bar-2013-07-02.functional" could not be opened: failed to open stream: No such file or directory
```