README example `qs.all().filter()` doesn't work

[dandavison]

>>> from mock_django.query import QuerySetMock

>>> qs = QuerySetMock(Post, 1, 2, 3)

>>> qs.all().filter()
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-14-4db5ce9e96fc> in <module>()
----> 1 qs.all().filter()

AttributeError: 'generator' object has no attribute 'filter'

[boydjj]

Yeah, I think I wrote that and shouldn't have. This is pretty much a dupe of #15.

[JamesBradbury-Abide]

I am also experiencing this issue with 0.6.10. I thought that #15 had been closed, so shouldn't this be working? Sorry if I've misunderstood how these things work.