Adding ability to dist freebsd, openbsd, netbsd, and plan9

Makefile

diff --git a/Makefile b/Makefile
index 7d777ce..a33f9b4 100644
--- a/Makefile
+++ b/Makefile
@@ -26,7 +26,7 @@
 build-all:
 	gox -verbose \
 	-ldflags "-X main.version=${VERSION}" \
-	-os="linux darwin windows " \
+	-os="linux darwin windows freebsd openbsd netbsd plan9" \
 	-arch="amd64 386 armv5 armv6 armv7 arm64" \
 	-osarch="!darwin/arm64" \
 	-output="dist/{{.OS}}-{{.Arch}}/{{.Dir}}" .