Update Dockerfile deps

* Updated dependencies (failed build without musl-dev)
* `AUTHOR` is apparently not valid, so `MAINTAINER` it is... (too late for this)
* Built and tested on `rpi-zero1.local` (needs script)

Dockerfile

@@ -1,8 +1,8 @@
 FROM armhf/alpine:3.5
-AUTHOR CD2Team <[email protected]>
+MAINTAINER CD2Team <[email protected]>
 
 RUN set -x \
-  && buildDeps='go git bzr' \
+  && buildDeps='go git bzr musl-dev' \
   && apk add --update $buildDeps \
   && GOPATH=/tmp/gocode go get github.com/mailhog/MailHog \
   && mv /tmp/gocode/bin/MailHog /usr/local/bin/ \