add viewset support

[sebdiem]

This is how I would solve issue #58.
I think that using the rest framework router, which provides all the magic, is probably the cleanest way.

[manosim]

Looks good to me! If someone else can review too that would be great! We can then merge and release to PyPI!

[preston-scibek]

Might I suggest adding to the documentation something about adding the following the urls.py if using viewsets and router?
url(r'^docs/', DRFDocsView.as_view(drf_router=router), name='drfdocs')

[egamonal]

@preston-scibek are you sure?

I added that line with the corresponding import from rest_framework_docs.views import DRFDocsView and I got an error:

TypeError: DRFDocsView() received an invalid keyword 'drf_router'. as_view only accepts arguments that are already attributes of the class.

[preston-scibek]

maybe it is just a bug on my local machine then, I had to do that to get it to work but if it's giving you an error, than it's most likely to do with my machine.
edit: By work, I mean to display urls that come from viewsets