Pep8ify examples

This PR converts the animation, api and axes_grid examples.

(Retry of #3182/#3183)

I addressed @ianthomas23' comments from #3183
Didn't a bunch of these files get changed during the SciPy sprints a few
months ago? Particularly with respect to spacing around operators? Or was
that in the codebase itself?

Also, now that these files have been PEP8-ified, I think there is some sort
of white-list or black-list in the testing directory that indicates which
files should be tested for pep8-compliance. This way the files stay pep8-ed.


On Thu, Aug 28, 2014 at 9:09 AM, Thomas Hisch <notifications@github.com>
wrote:

> In examples/api/collections_demo.py:
>
> > @@ -27,10 +27,10 @@
> >
> >  # Make some spirals
> >  r = np.array(range(nverts))
> > -theta = np.array(range(nverts)) * (2*np.pi)/(nverts-1)
> > +theta = np.array(range(nverts))*(2*np.pi)/(nverts - 1)
>
> np.linspace(0, 2*np.pi, nverts) would probably make this a lot clearer -
> @tacaswell <https://github.com/tacaswell> WDYT ?
>
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> <https://github.com/matplotlib/matplotlib/pull/3425/files#r16837317>.
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