DOC/WIP: travis notebook doc build
Just want to see the output log from the pull request.

https://travis-ci.org/pydata/pandas/jobs/139080123
 ## [Current coverage](https://codecov.io/gh/pydata/pandas/pull/13493?src=pr) is **84.33%**

> Merging [#13493](https://codecov.io/gh/pydata/pandas/pull/13493?src=pr) into [master](https://codecov.io/gh/pydata/pandas/branch/master?src=pr) will not change coverage

``` diff
@@             master     #13493   diff @@
==========================================
  Files           138        138          
  Lines         51106      51106          
  Methods           0          0          
  Messages          0          0          
  Branches          0          0          
==========================================
  Hits          43102      43102          
  Misses         8004       8004          
  Partials          0          0          
```

> Powered by [Codecov](https://codecov.io?src=pr). Last updated by [30d710f...df6939a](https://codecov.io/gh/pydata/pandas/compare/30d710f4c8a07cb7ea3bc91f6eb05c4bbdfa2f24...df6939a747ceeaf822faf2a83510175dbe0ef519)
 @jorisvandenbossche so my last commit succeeded https://travis-ci.org/pydata/pandas/jobs/139093566#L1569

I'm not sure why the `python -m ipykernel install` was necessary, I've never had to do that on my own system. I want to look into the correct way to do this, but won't have a chance till tonight or tomorrow.
 Hmm, I am not sure this is due to the installing of the kernel, as the logs say:

```
python -m ipykernel install
[Errno 13] Permission denied: '/usr/local/share/jupyter'
```

So I think it is just adding the `ipykernel` as dependency which was needed?
 Ahh, I missed that. Let me retry just using `notebook` to get everything like Jeff suggested.
 In principle, notebook is not needed (nbconvert and ipykernel should suffice as well), although doesn't hurt of course :-)
 Apart from the clean-up, I think this can be merged?
 @jorisvandenbossche fixed
 @jorisvandenbossche http://pandas-docs.github.io/pandas-docs-travis/style.html 🎉 

A few minor things, like dependencies on ipywidgets and seaborn didn't work. I can do another followup.
 Yes, we're coming closer :-)

Also a unicode thing (just needs a `u""` I think)
