Bump sphinx from 2.0.1 to 2.1.0 (#77)

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 2.0.1 to 2.1.0.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/master/CHANGES)
- [Commits](sphinx-doc/sphinx@v2.0.1...v2.1.0)

Author: dependabot-preview[bot]

poetry.lock

@@ -47,7 +47,7 @@ pytest = "^4.5"
 pytest-cov = "^2.7"
 pytest-randomly = "^3.0"
 
-sphinx = "^2.0"
+sphinx = "^2.1"
 sphinx-autodoc-typehints = "^1.6"
 sphinxcontrib-mermaid = "^0.3.1"
 sphinx-typlog-theme = "^0.7.1"