Set correct file name and dir on generated pages

Because Jekyll caches parsed templates by filename[1], not setting a
correct unique one will result in all generated pages being rendered
with the same template.

Fixes sverrirs#209.

[1] https://github.com/jekyll/jekyll/blob/67380a273888abaef96a1f37239e6a5f9eda8205/lib/jekyll/liquid_renderer/file.rb#L13

lib/jekyll-paginate-v2/generator/paginationModel.rb

@@ -268,8 +268,8 @@ def paginate(template, config, site_title, all_posts, all_tags, all_categories,
         newpages = []
 
         # Consider the default index page name and extension
-        indexPageName = config['indexpage'].nil? ? '' : config['indexpage'].split('.')[0]
-        indexPageExt =  config['extension'].nil? ? '' : Utils.ensure_leading_dot(config['extension'])
+        indexPageName = config['indexpage'].nil? ? 'index' : config['indexpage'].split('.')[0]
+        indexPageExt =  config['extension'].nil? ? '.html' : Utils.ensure_leading_dot(config['extension'])
         indexPageWithExt = indexPageName + indexPageExt
 
         # In case there are no (visible) posts, generate the index file anyway
@@ -308,6 +308,8 @@ def paginate(template, config, site_title, all_posts, all_tags, all_categories,
             newpage.set_url(newpage.pager.page_path+indexPageExt)
           end
 
+          newpage.dir = File.dirname(newpage.pager.page_path)
+
           if( template.data['permalink'] )
             newpage.data['permalink'] = newpage.pager.page_path
           end