update Dockerfile MAINTAINER

and also use what appears to be (based on some sampling of the docker
registry) the correct convention for specifying the email address.

Also ditch superfluous CMD instruction in weaver.

weavedns/Dockerfile

@@ -1,4 +1,5 @@
 FROM scratch
+MAINTAINER Weaveworks Inc <help@weave.works>
 WORKDIR /home/weave
 ADD ./weavedns /home/weave/
 EXPOSE 53/udp

weaver/Dockerfile

@@ -1,6 +1,5 @@
 FROM scratch
-MAINTAINER Zettio weave@zett.io
+MAINTAINER Weaveworks Inc <help@weave.works>
 WORKDIR /home/weave
 ADD ./weaver /home/weave/
-CMD []
 ENTRYPOINT ["/home/weave/weaver", "-iface", "ethwe", "-wait", "5"]