DOC: Updated links to 2 tutorials in tutorials.rst
Two of the links to the [pandas-cookbook](https://github.com/jvns/pandas-cookbook) did not work for version `v0.2` of the documents. Now all links work. Where a version  `v0.2` exists, it links to that version. In the remaining two cases, it now links to version `v0.1` instead of raising the `404: Page not found` error.
I would rather update the actual links and keep linking to the newer version, as those chapters still exist (the name was a bit changed): http://nbviewer.jupyter.org/github/jvns/pandas-cookbook/tree/master/cookbook/ # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/19857?src=pr&el=h1) Report
> Merging [#19857](https://codecov.io/gh/pandas-dev/pandas/pull/19857?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/ce77b79b97d7e827f50ebd0b7ca292fc2d966cc7?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/19857/graphs/tree.svg?token=eZ4WkYLtcO&width=650&src=pr&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/19857?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #19857   +/-   ##
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  Coverage   91.64%   91.64%           
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  Files         150      150           
  Lines       48946    48946           
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  Hits        44858    44858           
  Misses       4088     4088
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.02% <ø> (ø)` | :arrow_up: |
| #single | `41.81% <ø> (ø)` | :arrow_up: |


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 I agree @jorisvandenbossche. Thanks for reviewing! I have updated this PR:

- Every link is to `v2.0` now.
- Another chapter has been written (Chapter 9), I have added it.

And I believe this PR is good to go then. thanks!