Added Dockerfile

Dockerfile

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+#Each command creates a separate layer
+
+#Base subsquent layers on alpine:3.8
+FROM alpine:3.8
+
+#Create the /opt and /opt/app directories
+RUN mkdir /opt && mkdir /opt/app
+
+#Install python 3 and pip
+RUN apk add --no-cache python3 py-pip
+
+#Add the requirements file to /opt/app
+COPY requirements.txt /opt/app
+
+#pip install depedencies
+RUN pip3 install -r /opt/app/requirements.txt
+
+#Add the flask app to /opt/app
+COPY app.py /opt/app/app.py
+
+#Devleopment flask runs on port 5000. Expose.
+EXPOSE 5000
+
+#Set the flask app env var
+ENV FLASK_APP=/opt/app/app.py
+
+#Define the comamned to execute on container start. Must bind to all, not localhost or loopback
+CMD flask run --host=0.0.0.0