change dockerfile to python:slim

Dockerfile

@@ -1,7 +1,6 @@
-FROM debian:jessie
+FROM python:slim
 
-RUN apt-get update && apt-get install -y locales git build-essential \
-    python3 python3-pip python3-dev \
+RUN apt-get update && apt-get install -y git build-essential \
     libpq-dev libmysqlclient-dev libmemcached-dev libgeos-dev gettext \
     librsvg2-bin --no-install-recommends \
  && dpkg-reconfigure locales \
@@ -9,26 +8,17 @@ RUN apt-get update && apt-get install -y locales git build-essential \
  && /usr/sbin/update-locale LANG=C.UTF-8 \
  && apt-get clean \
  && rm -rf /var/lib/apt/lists/* \
- && useradd -ms /bin/bash -d /c3nav -u 15371 c3navuser \
  && mkdir /etc/c3nav && mkdir /data && mkdir /data/map
 
-ENV LC_ALL C.UTF-8
-
 COPY src /c3nav/src
 WORKDIR /c3nav/src
 
 COPY deployment/docker/c3nav.bash /usr/local/bin/c3nav
 
-RUN pip3 install -U pip wheel setuptools
-RUN pip3 install -r requirements.txt -r requirements/mysql.txt -r requirements/postgres.txt \
+RUN pip install -r requirements.txt -r requirements/mysql.txt -r requirements/postgres.txt \
 	-r requirements/memcached.txt -r requirements/redis.txt gunicorn \
  && mkdir /static \
- && chown -R c3navuser:c3navuser /static /c3nav /data \
  && chmod +x /usr/local/bin/c3nav
 
-USER c3navuser
-
-EXPOSE 8000
-
 ENTRYPOINT ["c3nav"]
 CMD ["all"]