add dockerfile for playground/minimal setup

docker_playground/Dockerfile

@@ -0,0 +1,22 @@
+FROM ruby:2.1.6
+
+# install redis
+RUN cd /usr/src \
+    && wget -c http://download.redis.io/redis-stable.tar.gz \
+    && tar xvzf redis-stable.tar.gz \
+    && cd redis-stable \
+    && make && make install \
+    &&  echo -ne '\n' | utils/install_server.sh
+
+# postgres client libs for streaming from redshift
+RUN apt-get update && apt-get install -y postgresql-client --no-install-recommends && rm -rf /var/lib/apt/lists/*
+
+# log location
+RUN mkdir -p /var/log/aleph
+ENV SERVER_LOG_ROOT /var/log/aleph
+
+# make temp writeable
+RUN chmod 777 /tmp
+
+RUN gem install aleph_analytics
+EXPOSE 3000