Drop Py37, improve typing and docstrings (#544)

Drops Py3.7, improves typing and adds a mypy config, improves the docstrings and isorts the imports.

* configure isort
* sort with isort
* add github action
* enable flake8-docstrings
* fix docstrings
* add mypy env
* no implicit optional
* add type for raw
* add some type hints

setup.py

@@ -1,9 +1,10 @@
 #!/usr/bin/env python
+"""Setup script for python package."""
 
 import os
 import sys
-from setuptools import find_packages, setup
 
+from setuptools import find_packages, setup
 
 base_dir = os.path.dirname(__file__)
 src_dir = os.path.join(base_dir, "src")
@@ -14,14 +15,18 @@ sys.path.insert(0, src_dir)
 
 
 def read(fname):
-    """read file from same path as setup.py"""
+    """Read file from same path as setup.py."""
     return open(os.path.join(os.path.dirname(__file__), fname)).read()
 
 
 setuptools_scm_template = """\
-# coding: utf-8
-# file generated by setuptools_scm
-# don't change, don't track in version control
+#!/usr/bin/python
+#  -*- coding: utf-8 -*-
+\"\"\"Version identifier.
+
+file generated by setuptools_scm
+don't change, don't track in version control
+\"\"\"
 
 version = '{version}'
 """