Fix ogp twitter card 2 (#277)

* site => creator

* Remove duplicate metadatas in twitter card and ogp

* Fix

* Fix

* Fix og:type

ref https://ogp.me

* Fix og:site_name

source/_meta_tags.erb

@@ -26,9 +26,9 @@
 
 <!-- ogp -->
 <meta property="og:title" content="<%= title %>">
-<meta property="og:type" content="<%= current_article.nil? ? 'article' : 'blog' %>">
+<meta property="og:type" content="<%= current_article.nil? ? 'website' : 'article' %>">
 <meta property="og:locale" content="ja_JP">
-<meta property="og:site_name" content="<%= "#{app.config.blog_title} : #{app.config.blog_subtitle}" %>">
+<meta property="og:site_name" content="<%= app.config.blog_title %>">
 <meta property="og:image" content="<%= app.config.url_root + image_path('/img/ikuwow_200x200.png')%>">
 <meta property="og:description" content="<%= description %>">
 <meta property="article:publisher" content="ikuwow">