match name of automated build base img

Dockerfile

@@ -1,4 +1,4 @@
-FROM mitmproxy/base:onbuild
+FROM mitmproxy/base:latest-onbuild
 EXPOSE 8080
 EXPOSE 8081
 VOLUME /certs

Dockerfile.base-onbuild

@@ -1,26 +0,0 @@
-FROM debian:jessie
-
-ENV DEBIAN_FRONTEND noninteractive
-ENV PYTHON /usr/bin/python2.7
-
-RUN apt-get update && \
-    apt-get install -qq -y --no-install-recommends \
-        build-essential \
-        python-pip \
-        python-dev \
-        python-setuptools \
-        libffi-dev \
-        libxml2-dev \
-        libxslt1-dev \
-        git \
-        zlib1g-dev \
-        libssl-dev && \
-    rm -rf /var/lib/apt/lists/*
-
-ENV LANG en_US.UTF-8
-ENV LC_ALL C.UTF-8
-
-ONBUILD ADD . /opt/mitmproxy
-ONBUILD WORKDIR /opt/mitmproxy
-ONBUILD RUN [ ! -e requirements.txt ] || pip install -r requirements.txt && \
-    rm -rf ~/.cache/pip /tmp/pip_build_root