Bump pytest from 3.6.3 to 3.6.4 in /{{cookiecutter.app_name}}

Bumps [pytest](https://github.com/pytest-dev/pytest) from 3.6.3 to 3.6.4.
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/master/CHANGELOG.rst)
- [Commits](https://github.com/pytest-dev/pytest/compare/3.6.3...3.6.4)

Signed-off-by: dependabot[bot] <support@dependabot.com>

{{cookiecutter.app_name}}/requirements/dev.txt

@@ -2,7 +2,7 @@
 -r prod.txt
 
 # Testing
-pytest==3.6.3
+pytest==3.6.4
 WebTest==2.0.30
 factory-boy==2.11.1