add Dockerfile to simplify installation

Dockerfile

@@ -0,0 +1,16 @@
+FROM python:3.4-slim
+WORKDIR /app
+COPY ./images /app/images
+COPY ./libgrabsite /app/libgrabsite
+COPY ./grab-site ./gs-dump-urls ./gs-server ./setup.py /app/
+RUN apt-get update && \
+    apt-get install -y build-essential && \
+    pip3 install ./ && \
+    apt-get purge -y build-essential && \
+    apt-get autoremove -y && \
+    apt-get clean && \
+    rm -R /root/.cache
+VOLUME ["/data"]
+WORKDIR /data
+EXPOSE 29000
+CMD ["python", "/app/gs-server"]