remove non-alphanumeric chars from item pretty urls

mainly because they were causing the router to freak out when they
contained periods, because that looks like a format, e.g. show.html

app/models/item.rb

@@ -156,8 +156,9 @@ class Item < ActiveRecord::Base
     }
   end
 
+  URL_CHAR_BLACKLIST = /[^a-z0-9\-]/i
   def name_for_url
-    name.downcase.gsub(' ', '-')
+    name.downcase.gsub(' ', '-').gsub(URL_CHAR_BLACKLIST, '')
   end
 
   def to_param

public/javascripts/wardrobe.js

@@ -126,7 +126,7 @@ function Wardrobe() {
     }
 
     function getNameForSlug() {
-      return item.name.toLowerCase().replace(/ /g, '-');
+      return item.name.toLowerCase().replace(/ /g, '-').replace(/[^a-z0-9\-]/i, '');
     }
 
     function getSlug() {