Bump test image to Python 3.7.3

... and remove some unnecessary comments from the CircleCI config.

Author: acrewdson

.circleci/config.yml

@@ -6,14 +6,7 @@ version: 2
 jobs:
   build:
     docker:
-      # specify the version you desire here
-      # use `-browsers` prefix for selenium tests, e.g. `3.6.1-browsers`
-      - image: circleci/python:3.6.1
-
-      # Specify service dependencies here if necessary
-      # CircleCI maintains a library of pre-built images
-      # documented at https://circleci.com/docs/2.0/circleci-images/
-      # - image: circleci/postgres:9.4
+      - image: circleci/python:3.7.3
 
     working_directory: ~/repo
 
@@ -39,11 +32,6 @@ jobs:
             - ./venv
           key: v1-dependencies-{{ checksum "requirements.txt" }}
 
-      # run tests!
-      # this example uses Django's built-in test-runner
-      # other common Python testing frameworks include pytest and nose
-      # https://pytest.org
-      # https://nose.readthedocs.io
       - run:
           name: run tests
           command: |