DOC: docs don't build with new Sphinx version 1.2
I always build the docs with Sphinx 1.1.3, but recently (in december) a new Sphinx version was released: 1.2. 

And it seems that the docs won't build with this new version (also mentioned in #5530 and https://github.com/pydata/pandas/pull/5701#discussion_r8715560). You get the following error:

```
  File "C:\Users\vdbosscj\Scipy\pandas-joris\doc\source\_templates\autosummary/class.rst", line 1, in top-level template code
    {% extends "!autosummary/class.rst" %}
  File "C:\Anaconda\envs\devel2\lib\site-packages\jinja2\utils.py", line 339, in get
    return self[key]
  File "C:\Anaconda\envs\devel2\lib\site-packages\jinja2\utils.py", line 389, in __getitem__
    if self._queue[-1] != key:
RuntimeError: maximum recursion depth exceeded in cmp
```

This has something to do with the class.rst template for autosummary (which we extend in [doc/source/_templates/autosummary/class.rst](https://github.com/pydata/pandas/blob/master/doc/source/_templates/autosummary/class.rst))

If you remove the template class.rst, the docs will build (you only will get a bunch of warnings because of links to non-existing documents, because not all docstring pages are built (that was the reason for the template)).
