slug should replace underscores

lib/slug.rb

@@ -6,7 +6,7 @@
 module Slug
 
   def self.for(string)
-    string.parameterize
+    string.parameterize.gsub("_", "-")
   end
 
 end

spec/components/slug_spec.rb

@@ -39,5 +39,9 @@ describe Slug do
     Slug.for(from).should == to
   end
 
+  it 'replaces underscores' do
+    Slug.for("o_o_o").should == "o-o-o"
+  end
+
 end