Use default version requirement '> 0' in setup.rake


git-svn-id: https://svn.apache.org/repos/asf/incubator/buildr/trunk@660781 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/rakelib/setup.rake b/rakelib/setup.rake
index 919800b..bd6a499 100644
--- a/rakelib/setup.rake
+++ b/rakelib/setup.rake
@@ -36,7 +36,7 @@
 end
 
 
-def install_gem(name, ver_requirement = nil)
+def install_gem(name, ver_requirement = ['> 0'])
   dep = Gem::Dependency.new(name, ver_requirement)
   rb_bin = File.join(Config::CONFIG['bindir'], Config::CONFIG['ruby_install_name'])
   if Gem::SourceIndex.from_installed_gems.search(dep).empty?