czmq: use spec deps

Formula/czmq.rb

@@ -2,18 +2,19 @@ require 'formula'
 
 class Czmq < Formula
   homepage 'http://czmq.zeromq.org/'
-  head 'https://github.com/zeromq/czmq.git'
   url 'http://download.zeromq.org/czmq-1.4.1.tar.gz'
   sha1 '8ddb485e9d53bca6bb703c850be40b8da70c4d74'
 
-  option :universal
+  head do
+    url 'https://github.com/zeromq/czmq.git'
 
-  if build.head?
     depends_on 'autoconf'
     depends_on 'automake'
     depends_on 'libtool'
   end
 
+  option :universal
+
   depends_on 'zeromq'
 
   def install