Fixes `link` tag to work with static files

lib/jekyll/tags/link.rb

@@ -18,6 +18,8 @@ module Jekyll
 
         site.each_site_file do |item|
           return item.url if item.relative_path == @relative_path
+          # This takes care of the case for static files that have a leading /
+          return item.url if item.relative_path == "/#{@relative_path}"
         end
 
         raise ArgumentError, <<eos

test/test_tags.rb

@@ -637,6 +637,7 @@ title: linking
 
 {% link contacts.html %}
 {% link info.md %}
+{% link /css/screen.css %}
 CONTENT
       create_post(content, {
         "source"      => source_dir,
@@ -656,6 +657,10 @@ CONTENT
     should "have the URL to the \"info\" item" do
       assert_match(%r!/info\.html!, @result)
     end
+
+    should "have the URL to the \"screen.css\" item" do
+      assert_match(%r!/css/screen\.css!, @result)
+    end
   end
 
   context "simple page with linking" do