Added nodejs, use docker ubuntu image

Dockerfile

@@ -1,9 +1,9 @@
-FROM registry.docker-cn.com/library/ubuntu:16.04
+FROM ubuntu:16.04
 
 COPY build/java_policy /etc
 
 RUN buildDeps='software-properties-common git libtool cmake python-dev python3-pip python-pip libseccomp-dev' && \
-    apt-get update && apt-get install -y python python3.5 python-pkg-resources python3-pkg-resources gcc g++ $buildDeps && \
+    apt-get update && apt-get install -y nodejs python python3.5 python-pkg-resources python3-pkg-resources gcc g++ $buildDeps && \
     add-apt-repository ppa:openjdk-r/ppa && apt-get update && apt-get install -y openjdk-8-jdk && \
     pip3 install --no-cache-dir psutil gunicorn flask requests && \
     cd /tmp && git clone -b newnew  --depth 1 https://github.com/QingdaoU/Judger && cd Judger && \