Switch to twine in tox.ini as recommended to check the rst doc.

[aerostitch]

When running the readme and sanity targets you can see the following message:

readme runtests: commands[0] | python setup.py check --restructuredtext --strict
running check
warning: Check: This command has been deprecated. Use `twine check` instead: https://packaging.python.org/guides/making-a-pypi-friendly-readme#validating-restructuredtext-markup
The project's long description is valid RST.

This PR switches the check to twine as recommended.

[coveralls]

Pull Request Test Coverage Report for Build 557

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 87.697%

---

Totals
Change from base Build 550:	0.0%
Covered Lines:	613
Relevant Lines:	699

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 557

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 87.697%

---

Totals
Change from base Build 550:	0.0%
Covered Lines:	613
Relevant Lines:	699

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 557

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 87.697%

---

Totals
Change from base Build 550:	0.0%
Covered Lines:	613
Relevant Lines:	699

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 558

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 87.697%

---

Totals
Change from base Build 550:	0.0%
Covered Lines:	613
Relevant Lines:	699

---

💛 - Coveralls

[atodorov]

Thanks for the PR, generally looks good and I'm all for using the latest tools.

However I get the following message from Travis:

/home/travis/build/PyCQA/pylint-django/.tox/readme/lib/python3.6/site-packages/readme_renderer/markdown.py:38: UserWarning: Markdown renderers are not available. Install 'readme_render[md]' to enable Markdown rendering.

Also I tried twine check locally (on another project though) and it complained about the same missing pieces.

Also the package name in the message is wrong and the correct one is readme-renderer[md]

[atodorov]

Scratch my previous comment. I just realized we use rst here and readme-renderer gets installed as dependency to twine.