[mc] Add dinnerbone's mcstatus and use it for HEALTHCHECK

Part of #159

minecraft-server/Dockerfile

@@ -16,9 +16,13 @@ RUN echo "http://dl-3.alpinelinux.org/alpine/v3.5/community/" >> /etc/apk/reposi
           git \
           jq \
           mysql-client \
-          python python-dev && \
+          python python-dev py2-pip && \
         rm -rf /var/cache/apk/*
 
+RUN pip install mcstatus
+
+HEALTHCHECK CMD mcstatus localhost ping
+
 RUN addgroup -g 1000 minecraft \
   && adduser -Ss /bin/false -u 1000 -G minecraft -h /home/minecraft minecraft \
   && mkdir /data \