Use Flask for Python environment

Flask gives us easy routing support, and simple interface for getting
at request data.

environments/python3/Dockerfile

@@ -1,3 +1,12 @@
-FROM python:3-onbuild
-CMD [ "python", "./server.py" ]
-EXPOSE 8888
+FROM ubuntu:16.04
+
+RUN apt-get update -y
+RUN apt-get install -y python3 python3-pip python3-dev build-essential
+
+COPY . /app
+WORKDIR /app
+RUN pip3 install -r requirements.txt
+
+ENTRYPOINT ["python3"]
+CMD ["server.py"]
+