Scheduled weekly dependency update for week 06 (#203)

* Update wheel from 0.36.1 to 0.36.2

* Update tox from 3.20.1 to 3.21.4

* Update coverage from 5.3 to 5.4

* Update sphinx from 3.3.1 to 3.4.3

* Update sphinx-rtd-theme from 0.5.0 to 0.5.1

* Update cryptography from 3.2.1 to 3.4.1

requirements_dev.txt

@@ -1,8 +1,8 @@
 bumpversion==0.6.0
-wheel==0.36.1
+wheel==0.36.2
 flake8==3.8.4
-tox==3.20.1
-coverage==5.3
-Sphinx==3.3.1
-sphinx-rtd-theme==0.5.0
-cryptography==3.2.1
+tox==3.21.4
+coverage==5.4
+Sphinx==3.4.3
+sphinx-rtd-theme==0.5.1
+cryptography==3.4.1