Update sphinx from 1.8.5 to 3.0.4

requirements.txt

@@ -54,7 +54,7 @@ ruamel.yaml==0.16.0       # via strictyaml
 setuptools-scm==3.3.3
 six==1.12.0               # via argon2-cffi, mock, more-itertools, packaging, pytest, python-dateutil, sphinx, tox
 snowballstemmer==1.9.0    # via sphinx
-sphinx==1.8.5
+sphinx==3.0.4
 sphinxcontrib-websupport==1.1.2  # via sphinx
 strictyaml==1.0.3         # via devpi-server
 toml==0.10.0              # via check-manifest, tox