[ISSUE-3/4] Adds test container and tooling (#8)

* Adding black, isort, and flake8 to pytest

* Applying black, flake8, and isort to codebase

docker-compose.override.yml

@@ -0,0 +1,24 @@
+version: "3.7"
+
+services:
+  tests:
+    build: .
+    environment:
+      - TEST_DATABASE_URL=postgres://admin:password@database:5432/cbwebreader_test
+      - DJANGO_SETTINGS_MODULE=cbreader.settings.base
+    links:
+      - database
+    command: >
+      pytest
+              -vvv
+              --isort
+              --flake8
+              --black
+              --cov=.
+              --cov-report=term-missing
+              --junitxml=/tmp/test-results.xml
+    volumes:
+      - ./cbreader:/src/cbreader
+      - ./comic:/src/comic
+      - ./comic_auth:/src/comic_auth
+      - ${COMIC_BOOK_VOLUME}:/data