add jekyll version to the drop

lib/jekyll-seo-tag/drop.rb

@@ -20,6 +20,10 @@ module Jekyll
         Jekyll::SeoTag::VERSION
       end
 
+      def jekyll_version
+        Jekyll::VERSION
+      end
+
       # Should the `<title>` tag be generated for this page?
       def title?
         return false unless title

lib/template.html

@@ -3,7 +3,7 @@
   <title>{{ seo_tag.title }}</title>
 {% endif %}
 
-<meta name="generator" content="Jekyll v{{ jekyll.version }}" />
+<meta name="generator" content="Jekyll v{{ seo_tag.jekyll_version }}" />
 
 {% if seo_tag.page_title %}
   <meta property="og:title" content="{{ seo_tag.page_title }}" />