Format and lint codes and fix packaging (#125)

* add: configure files (setup.py->setup.py+setup.cfg+pyproject.toml)

* add: __download_url__

* format with black and isort

* fix: flake8 section in setup.cfg

* add: E501 to flake ignore

* fix: metadata.name does not accept attr

* fix: merge __version__.py into __init__.py

* fix: flake8 errors in tests/

* fix: datetime.datetime -> datetime

* fix: banner

* fix: ignore W605 for banner

* fix: way to install deps in CI

* add: versem to setuptools

* fix: drop python<=3.6 (#126) from package and CI

tests/test_availability_api.py

@@ -1,21 +1,24 @@
-import pytest
 import random
 import string
 from datetime import datetime, timedelta
 
+import pytest
+
 from waybackpy.availability_api import WaybackMachineAvailabilityAPI
 from waybackpy.exceptions import (
-    InvalidJSONInAvailabilityAPIResponse,
     ArchiveNotInAvailabilityAPIResponse,
+    InvalidJSONInAvailabilityAPIResponse,
 )
 
 now = datetime.utcnow()
 url = "https://example.com/"
 user_agent = "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.99 Safari/537.36"
 
-rndstr = lambda n: "".join(
-    random.choice(string.ascii_uppercase + string.digits) for _ in range(n)
-)
+
+def rndstr(n):
+    return "".join(
+        random.choice(string.ascii_uppercase + string.digits) for _ in range(n)
+    )
 
 
 def test_oldest():
@@ -57,7 +60,7 @@ def test_invalid_json():
     """
     with pytest.raises(InvalidJSONInAvailabilityAPIResponse):
         availability_api = WaybackMachineAvailabilityAPI(url="", user_agent=user_agent)
-        archive_url = availability_api.archive_url
+        _ = availability_api.archive_url
 
 
 def test_no_archive():
@@ -73,7 +76,7 @@ def test_no_archive():
         availability_api = WaybackMachineAvailabilityAPI(
             url="https://%s.cn" % rndstr(30), user_agent=user_agent
         )
-        archive_url = availability_api.archive_url
+        _ = availability_api.archive_url
 
 
 def test_no_api_call_str_repr():