pax-runner: spell out URL

Upcoming changes to formula specs may forbid using a class instance
variable in this manner, and it's easier to copy/paste anyway.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>

Formula/pax-runner.rb

@@ -1,9 +1,9 @@
 require 'formula'
 
 class PaxRunner < Formula
-  version '1.7.6'
-  url 'http://repo1.maven.org/maven2/org/ops4j/pax/runner/pax-runner-assembly/'+ version + '/pax-runner-assembly-' + version + '-jdk15.tar.gz'
   homepage 'http://team.ops4j.org'
+  url 'http://repo1.maven.org/maven2/org/ops4j/pax/runner/pax-runner-assembly/1.7.6/pax-runner-assembly-1.7.6-jdk15.tar.gz'
+  version '1.7.6'
   md5 'f8bd2e0a902626baa58ae5a9df97b8e6'
 
   def install