Skip pb files in linters

In isort, black, and flake8, respectively.

Add `format` in Makefile

Run top level packages only

With `setup.py`, to avoid running other unrelated directories.

Refactor

pyproject.toml

@@ -0,0 +1,22 @@
+[tool.black]
+line-length = 88
+target_version = ['py37']
+include = '\.pyi?$'
+exclude = '''
+
+(
+  /(
+      \.eggs         # exclude a few common directories in the
+    | \.git          # root of the project
+    | \.hg
+    | \.mypy_cache
+    | \.tox
+    | \.venv
+    | _build
+    | buck-out
+    | build
+    | dist
+  )/
+  | \w*_pb2\w*\.py  # pb2 files
+)
+'''