Add pre-commit config

.pre-commit-config.yaml

@@ -0,0 +1,15 @@
+repos:
+- repo: https://github.com/ambv/black
+  rev: 18.9b0
+  hooks:
+  - id: black
+
+- repo: https://github.com/pre-commit/pre-commit-hooks
+  rev: v2.1.0
+  hooks:
+  - id: flake8
+
+- repo: https://github.com/asottile/reorder_python_imports
+  rev: v1.3.5
+  hooks:
+  - id: reorder-python-imports