Add dockerfile for raspberry build

rpi-Dockerfile

@@ -0,0 +1,41 @@
+FROM resin/rpi-raspbian
+
+# less priviledge user, the id should map the user the downloaded files belongs to
+RUN groupadd -r aria && useradd -r -g aria aria -u 1000
+
+# webui + aria2
+RUN apt-get update \
+        && apt-get install -y aria2 busybox curl git \
+        && rm -rf /var/lib/apt/lists/*
+
+ADD . /webui-aria2
+
+# gosu install latest
+RUN GITHUB_REPO="https://github.com/tianon/gosu" \
+  && LATEST=`curl -s  $GITHUB_REPO"/releases/latest" | grep -Eo "[0-9].[0-9]*"` \
+  && curl -L $GITHUB_REPO"/releases/download/"$LATEST"/gosu-armhf" > /usr/local/bin/gosu \
+  && chmod +x /usr/local/bin/gosu
+
+# goland install (compile source code for ARM since no version are currently available)
+RUN curl -L "https://storage.googleapis.com/golang/go1.6.1.linux-armv6l.tar.gz" > go.tar.gz \
+  && tar -xzf go.tar.gz -C /usr/local \
+  && export GOROOT="/usr/local/go" && export GOPATH=`pwd` \
+  && $GOROOT/bin/go get github.com/mattn/goreman && $GOROOT/bin/go build -o /usr/local/bin/goreman github.com/mattn/goreman \
+  && apt-get remove purge --auto-remove git \
+  && rm go.tar.gz && rm -rf $GOROOT && rm -rf $GOPATH/src && rm -rf $GOPATH/pkg \
+  && unset GOROOT && unset GOPATH
+
+# goreman setup
+RUN echo "web: gosu aria /bin/busybox httpd -f -p 8080 -h /webui-aria2\nbackend: gosu aria /usr/bin/aria2c --conf-path=/data/.aria2/aria2.conf" > Procfile
+
+# aria2 downloads directory
+VOLUME /data
+
+# aria2 RPC port, map as-is or reconfigure webui
+EXPOSE 6800/tcp
+
+# webui static content web server, map wherever is convenient
+EXPOSE 8080/tcp
+
+CMD ["start"]
+ENTRYPOINT ["/usr/local/bin/goreman"]