Add pyupgrade and black formatter pre-commit hooks, remove autopep8 as obviated by black.

Author: Daniel Gallagher

.pre-commit-config.yaml

@@ -1,18 +1,23 @@
+repos:
 -   repo: git://github.com/pre-commit/pre-commit-hooks
-    sha: v0.8.0
+    rev: v1.3.0
     hooks:
-    -   id: autopep8-wrapper
-        args:
-        - -i
-        - --ignore=E128,E309,E501
-        exclude: ^docs/.*$
     -   id: check-json
     -   id: check-yaml
     -   id: debug-statements
     -   id: end-of-file-fixer
         exclude: ^docs/.*$
     -   id: trailing-whitespace
+        exclude: README.md
     -   id: pretty-format-json
         args:
         - --autofix
-        - --indent=4
+-   repo: https://github.com/asottile/pyupgrade
+    rev: v1.2.0
+    hooks:
+    -   id: pyupgrade
+-   repo: https://github.com/ambv/black
+    rev: stable
+    hooks:
+    - id: black
+      language_version: python3.6