Add docker-compose support (#545)

Dockerfile

@@ -1,9 +1,13 @@
 # Docker support, thanks to xinyifly
 
-FROM openjdk:7-alpine
+FROM openjdk:8u171-jdk-alpine
 RUN apk -U add tini
 WORKDIR /mnt
 COPY ./ ./
 RUN sh ./posix-compile.sh
+ADD https://github.com/ufoscout/docker-compose-wait/releases/download/2.6.0/wait /wait
+RUN chmod +x /wait
+
 EXPOSE 8484 7575 7576 7577
-CMD exec tini -- sh ./posix-launch.sh
+ENTRYPOINT ["tini", "--"]
+CMD /wait && sh ./posix-launch.sh