Update pytest to 3.7.4 (#27)

This PR updates [pytest](https://pypi.org/project/pytest) from **3.7.3** to **3.7.4**.



<details>
  <summary>Changelog</summary>
  
  
   ### 3.7.4
   ```
   =========================

Bug Fixes
---------

- `3506 &lt;https:/pytest-dev/pytest/issues/3506&gt;`_: Fix possible infinite recursion when writing ``.pyc`` files.


- `3853 &lt;https:/pytest-dev/pytest/issues/3853&gt;`_: Cache plugin now obeys the ``-q`` flag when ``--last-failed`` and ``--failed-first`` flags are used.


- `3883 &lt;https:/pytest-dev/pytest/issues/3883&gt;`_: Fix bad console output when using ``console_output_style=classic``.


- `3888 &lt;https:/pytest-dev/pytest/issues/3888&gt;`_: Fix macOS specific code using ``capturemanager`` plugin in doctests.



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

- `3902 &lt;https:/pytest-dev/pytest/issues/3902&gt;`_: Fix pytest.org links
   ```
   
  
</details>


 

<details>
  <summary>Links</summary>
  
  - PyPI: https://pypi.org/project/pytest
  - Changelog: https://pyup.io/changelogs/pytest/
  - Homepage: https://docs.pytest.org/en/latest/
</details>

requirements.txt

@@ -2,4 +2,4 @@ flake8==3.5.0
 httplib2==0.11.3
 jsonschema==2.6.0
 markdown-generator==0.1.3
-pytest==3.7.3
+pytest==3.7.4