Update build.jl

Change homebrew package name from `zeromq` -> `zeromq32`, now that zeromq 4.0 is out.

Note that the `zeromq` package will still work, it will just constantly tell users that it's outdated, because Homebrew expects version 4.0 to be installed, not 3.2.4.  (I force it to install 3.2.4 if a package asks for just plain old `zeromq`, so things are always functional)

deps/build.jl

@@ -15,7 +15,7 @@ end
     if Pkg.installed("Homebrew") === nothing
         error("Homebrew package not installed, please run Pkg.add(\"Homebrew\")")  end
     using Homebrew
-    provides( Homebrew.HB, "zeromq", zmq, os = :Darwin )
+    provides( Homebrew.HB, "zeromq32", zmq, os = :Darwin )
 end
 
 @BinDeps.install [:zmq => :zmq]