Update circleci config to test 3.8 and 3.9

Author: Maciej Rapacz

.circleci/config.yml

@@ -13,20 +13,15 @@ jobs:
             pip install tox
             curl -sSL https://raw.githubusercontent.com/python-poetry/poetry/master/get-poetry.py | python -
             source "${HOME}/.profile"
-            make test
-  build-py36:
+            make
+  build-py39:
     <<: *base_template
     docker:
-      - image: python:3.6
-  build-py37:
-    <<: *base_template
-    docker:
-      - image: python:3.7
+      - image: python:3.9
   build-py38: *base_template
 workflows:
   version: 2
   build:
     jobs:
-      - build-py36
-      - build-py37
       - build-py38
+      - build-py39