Use releases in Dockerfile

.gitignore

@@ -1,4 +1,5 @@
 runsvinit
+runsvinit-*-*
 
 # Compiled Object files, Static and Dynamic libs (Shared Objects)
 *.o

example/Dockerfile

@@ -11,5 +11,6 @@ ADD bar /
 RUN mkdir -p /etc/service/bar
 ADD run-bar /etc/service/bar/run
 
-ADD runsvinit /
+ADD https://github.com/peterbourgon/runsvinit/releases/download/v1.0.0/runsvinit-linux-amd64.tgz /
+RUN tar zxf /runsvinit-linux-amd64.tgz && mv /runsvinit-linux-amd64 /runsvinit
 ENTRYPOINT ["/runsvinit"]