jython: use install_symlink

Formula/jython.rb

@@ -1,14 +1,13 @@
 require 'formula'
 
 class Jython < Formula
+  homepage 'http://www.jython.org'
   url "http://downloads.sourceforge.net/project/jython/jython/2.5.2/jython_installer-2.5.2.jar",
     :using => :nounzip
-  homepage 'http://www.jython.org'
   sha1 'd4534a691edf40aa1d51723dfe3e22db1e39b432'
 
   def install
-    system "java", "-jar", Pathname.new(@url).basename, "-s", "-d", libexec
-    bin.mkpath
-    ln_s libexec+'bin/jython', bin
+    system "java", "-jar", "jython_installer-2.5.2.jar", "-s", "-d", libexec
+    bin.install_symlink libexec+'bin/jython'
   end
 end