Add `bibiliography_list_attributes` and `bibliography_tag_attributes` options

This permits custom attributes to be passed to the bibliography list
such as `reversed` or `start` to permit custom numbering.

See inukshuk#148

lib/jekyll/scholar/defaults.rb

@@ -11,6 +11,8 @@ module Jekyll
       'bibliography_group_tag' => 'h2,h3,h4,h5',
       'bibliography_list_tag'  => 'ol',
       'bibliography_item_tag'  => 'li',
+      'bibliography_list_attributes' => {},
+      'bibliography_item_attributes' => {},
 
       'source'                 => './_bibliography',
       'bibliography'           => 'references.bib',

lib/jekyll/scholar/tags/bibliography.rb

@@ -89,10 +89,12 @@ module Jekyll
               config['details_link'], :class => config['details_link_class'])
           end
 
-          content_tag config['bibliography_item_tag'], reference
+          content_tag config['bibliography_item_tag'], reference, config['bibliography_item_attributes']
         }.join("\n")
 
-        content_tag config['bibliography_list_tag'], bibliography, :class => config['bibliography_class']
+        content_tag config['bibliography_list_tag'], bibliography,
+          { :class => config['bibliography_class'] }.merge(config['bibliography_list_attributes'])
+
       end
       
     end