refactor: docker image layout

docker/spleeter.dockerfile

@@ -0,0 +1,16 @@
+ARG BASE=python:3.6
+ARG SPLEETER_PACKAGE=spleeter
+ARG SPLEETER_VERSION=1.4.9
+
+FROM ${BASE}
+
+ENV MODEL_PATH /model
+
+RUN mkdir -p /model
+COPY audio_example.mp3 .
+
+RUN apt-get update && apt-get install -y ffmpeg libsndfile1
+RUN pip install musdb museval
+RUN pip install ${SPLEETER_PACKAGE}==${SPLEETER_VERSION}
+
+ENTRYPOINT ["spleeter"]