Updated recipes for Dockerfile and tox and instructions for coverage

- Sample configuration of coveragerc: https://git.io/fjZEl
- Pytest setup tips: https://bit.ly/2VKOAW1

.coveragerc

@@ -0,0 +1,11 @@
+[run]
+omit =
+    .venv/*
+    .tox/*
+    scripts/*
+    tests/*
+    */tests/*
+    */migrations/*
+
+[report]
+show_missing = True

Dockerfile

@@ -4,5 +4,6 @@ WORKDIR /app
 
 COPY . /app
 
-RUN pip install pipenv && \
+RUN python -m pip install --upgrade pip && \
+    pip install pipenv && \
     pipenv install --system --deploy --ignore-pipfile

tox.ini

@@ -8,4 +8,4 @@ deps = pipenv
 commands =
     pipenv install --dev --ignore-pipfile
     python manage.py makemigrations
-    pytest -vv --cov-report xml --cov=.
+    pytest tests -vv --doctest-modules --junitxml=junit/test-results.xml --cov=. --cov-report=xml --cov-report=html