Update dependencies via pyup (#204)

* Update tox from 3.1.2 to 3.2.1 (#203)
* Pin pre-commit to latest version 1.10.5 (#200)
* Update tox from 3.0.0 to 3.1.3 (#197)
* Update pytest from 3.6.3 to 3.7.1 (#195)

requirements_dev.txt

@@ -4,7 +4,7 @@ wheel==0.31.1
 watchdog==0.8.3
 flake8==3.5.0
 mock==2.0.0
-tox==3.1.2
+tox==3.2.1
 coverage==4.5.1
 Sphinx==1.7.6
 cryptography==2.3
@@ -13,6 +13,6 @@ future==0.16.0
 scipy>=0.17.0
 numpy>=1.13.0
 matplotlib>=1.3.1
-pytest==3.6.4
+pytest==3.7.1
 attrs==18.1.0
-pre-commit
+pre-commit==1.10.5