message: bugfix: change docker build from centos:centos7
diff: -FROM centos:7
  -
  -LABEL maintainer="SvenDowideit@home.org.au, zhangshaomin_1990@126.com"
  -
  -ENV PIKA /pika
  -ENV PIKA_BUILD_DIR /tmp/pika
  -ENV PATH ${PIKA}/bin:${PATH}
  -
  -COPY . ${PIKA_BUILD_DIR}
  -
  -WORKDIR ${PIKA_BUILD_DIR}
  +FROM centos:centos7
  +MAINTAINER left2right <yqzhang@easemob.com>
  RUN rpm -ivh https://mirrors.ustc.edu.cn/epel/epel-release-latest-7.noarch.rpm && \
  yum -y makecache && \
  