Configure pre-commit hooks and make them a dev dependency

.pre-commit-config.yaml

@@ -0,0 +1,5 @@
+repos:
+- repo: https://github.com/ambv/black
+  rev: 18.9b0
+  hooks:
+  - id: black

dev-requirements.txt

@@ -1,6 +1,7 @@
-# Note that there is also a Pipfile for this project if you are updating this 
+# Note that there is also a Pipfile for this project if you are updating this
 # file do not forget to update the Pipfile accordingly
 pyyaml
 pytest>=3.6
 wheel
 pytest-cov
+pre-commit