Update rrdtool to 1.4.3.

Also adds a (failing) test for the Ruby support.

Formula/rrdtool.rb

@@ -1,9 +1,9 @@
 require 'formula'
 
 class Rrdtool <Formula
-  url 'http://oss.oetiker.ch/rrdtool/pub/rrdtool-1.4.2.tar.gz'
+  url 'http://oss.oetiker.ch/rrdtool/pub/rrdtool-1.4.3.tar.gz'
   homepage 'http://oss.oetiker.ch/rrdtool/index.en.html'
-  md5 '9318d3b4016dd9dd9897f1eac7548032'
+  md5 '492cf946c72f85987238faa2c311b7bb'
 
   depends_on 'pkg-config'
   depends_on 'glib'
@@ -14,14 +14,24 @@ class Rrdtool <Formula
   depends_on 'libpng'
   depends_on 'intltool'
 
+  # Can use lua if it is found, but don't force users to install
+  # depends_on 'lua' => :optional
+
   def install
     system "./configure", "--disable-dependency-tracking",
                           "--prefix=#{prefix}",
-                          "--enable-perl-site-install", "--enable-ruby-site-install",
+                          "--enable-perl-site-install",
+                          "--enable-ruby-site-install",
                           # Installing directly into Homebrew's Python's site-packages
                           # can break things, so we disable this for now.
                           # TODO: how to build Python support w/o installing it.
                           "--disable-python"
+
     system "make install"
   end
+
+  def test
+    # Test ruby support; currently fails.
+    system "ruby", "-e", "require 'RRD'"
+  end
 end