Scheduled monthly dependency update for March (#23)

### Update [pip](https://pypi.org/project/pip) from **19.0.1** to **19.0.3**.


<details>
  <summary>Changelog</summary>
  
  
   ### 19.0.3
   ```
   ===================

Bug Fixes
---------

- Fix an ``IndexError`` crash when a legacy build of a wheel fails. (`6252 &lt;https://github.com/pypa/pip/issues/6252&gt;`_)
- Fix a regression introduced in 19.0.2 where the filename in a RECORD file
  of an installed file would not be updated when installing a wheel. (`6266 &lt;https://github.com/pypa/pip/issues/6266&gt;`_)
   ```
   
  
  
   ### 19.0.2
   ```
   ===================

Bug Fixes
---------

- Fix a crash where PEP 517-based builds using ``--no-cache-dir`` would fail in
  some circumstances with an ``AssertionError`` due to not finalizing a build
  directory internally. (`6197 &lt;https://github.com/pypa/pip/issues/6197&gt;`_)
- Provide a better error message if attempting an editable install of a
  directory with a ``pyproject.toml`` but no ``setup.py``. (`6170 &lt;https://github.com/pypa/pip/issues/6170&gt;`_)
- The implicit default backend used for projects that provide a ``pyproject.toml``
  file without explicitly specifying ``build-backend`` now behaves more like direct
  execution of ``setup.py``, and hence should restore compatibility with projects
  that were unable to be installed with ``pip`` 19.0. This raised the minimum
  required version of ``setuptools`` for such builds to 40.8.0. (`6163 &lt;https://github.com/pypa/pip/issues/6163&gt;`_)
- Allow ``RECORD`` lines with more than three elements, and display a warning. (`6165 &lt;https://github.com/pypa/pip/issues/6165&gt;`_)
- ``AdjacentTempDirectory`` fails on unwritable directory instead of locking up the uninstall command. (`6169 &lt;https://github.com/pypa/pip/issues/6169&gt;`_)
- Make failed uninstalls roll back more reliably and better at avoiding naming conflicts. (`6194 &lt;https://github.com/pypa/pip/issues/6194&gt;`_)
- Ensure the correct wheel file is copied when building PEP 517 distribution is built. (`6196 &lt;https://github.com/pypa/pip/issues/6196&gt;`_)
- The Python 2 end of life warning now only shows on CPython, which is the
  implementation that has announced end of life plans. (`6207 &lt;https://github.com/pypa/pip/issues/6207&gt;`_)

Improved Documentation
----------------------

- Re-write README and documentation index (`5815 &lt;https://github.com/pypa/pip/issues/5815&gt;`_)
   ```
   
  
</details>


 

<details>
  <summary>Links</summary>
  
  - PyPI: https://pypi.org/project/pip
  - Changelog: https://pyup.io/changelogs/pip/
  - Homepage: https://pip.pypa.io/
</details>





### Update [wheel](https://pypi.org/project/wheel) from **0.32.3** to **0.33.1**.


<details>
  <summary>Changelog</summary>
  
  
   ### 0.33.1
   ```
   - Fixed the ``--build-number`` option for ``wheel pack`` not being applied
   ```
   
  
  
   ### 0.33.0
   ```
   - Added the ``--build-number`` option to the ``wheel pack`` command
- Fixed bad shebangs sneaking into wheels
- Fixed documentation issue with ``wheel pack`` erroneously being called
  ``wheel repack``
- Fixed filenames with &quot;bad&quot; characters (like commas) not being quoted in
  ``RECORD`` (PR by Paul Moore)
- Sort requirements extras to ensure deterministic builds
  (PR by PoncinMatthieu)
   ```
   
  
</details>


 

<details>
  <summary>Links</summary>
  
  - PyPI: https://pypi.org/project/wheel
  - Changelog: https://pyup.io/changelogs/wheel/
  - Repo: https://github.com/pypa/wheel
</details>





### Update [PyYAML](https://pypi.org/project/PyYAML) from **4.2b4** to **5.1b3**.


*The bot wasn't able to find a changelog for this release. [Got an idea?](https://github.com/pyupio/changelogs/issues/new)*

<details>
  <summary>Links</summary>
  
  - PyPI: https://pypi.org/project/pyyaml
  - Homepage: http://pyyaml.org/wiki/PyYAML
</details>

requirements_dev.txt

@@ -1,13 +1,13 @@
-pip==19.0.1
+pip==19.0.3
 bumpversion==0.5.3
-wheel==0.32.3
+wheel==0.33.1
 watchdog==0.9.0
 flake8>=2.6.0
 tox==3.7.0
 coverage==4.5.2
 Sphinx>=1.6
 cryptography>2.3
-PyYAML==4.2b4
+PyYAML==5.1b3
 requests>=2.7.0
 lxml>=1.3