Add Dockerfile

Dockerfile

+FROM python:3.7
+
+WORKDIR /usr/src/app
+
+COPY requirements.txt ./
+RUN pip install --no-cache-dir -r requirements.txt
+
+COPY . .
+
+EXPOSE 5000
+
+ENV FLASK_ENV production
+ENV FLASK_RUN_HOST 0.0.0.0
+ENV DATABASE_USER dbuser
+ENV DATABASE_PASSWORD secret
+ENV DATABASE_NAME db
+ENV DATABASE_HOST postgresql
+
+CMD [ "flask", "run" ]