Introduce i18n for credits

Author: stomar

_config.yml

@@ -84,3 +84,12 @@ top_projects:
       applications. It is a Ruby library that works with Internet Explorer
       and Firefox.
 
+
+# Localization
+
+credits:
+  en: This website was generated with Ruby using <a href="http://www.jekyllrb.com/">Jekyll</a>.
+      It is proudly maintained by <a href="http://rubyidentity.org">members of the Ruby community</a>.
+      Please contact our <a href="mailto:[email protected]">webmaster</a>
+      for questions or comments concerning this website.
+

_includes/footer.html

@@ -1,5 +1,7 @@
-<p>Content available in <a href="/en/">English</a>, <a href="/fr/">French</a>, <a href="/ja/">Japanese</a>, <a href="/ko/">Korean</a>, <a href="/pl/">Polish</a>, <a href="/es/">Spanish</a>, <a href="/pt/">Portuguese</a>, <a href="/zh_cn/">Simplified Chinese</a>, <a href="/zh_TW/">Traditional Chinese</a>, <a href="/id/">Bahasa Indonesia</a>, <a href="/de/">German</a>, <a href="/it/">Italian</a>, <a href="/cs/">Czech</a>, <a href="/bg/">Bulgarian</a> and <a href="/tr/">Turkish</a>.</p> 
-<p>This website is was generated by <a href="http://www.jekyllrb.com/">Jekyll</a>.
-It is proudly maintained by <a href="http://rubyidentity.org">members of the Ruby community</a>. Please contact
-our <a href="mailto:[email protected]">webmaster</a> for questions or comments
-concerning this website.</p>
+<p>Content available in <a href="/en/">English</a>, <a href="/fr/">French</a>, <a href="/ja/">Japanese</a>, <a href="/ko/">Korean</a>, <a href="/pl/">Polish</a>, <a href="/es/">Spanish</a>, <a href="/pt/">Portuguese</a>, <a href="/zh_cn/">Simplified Chinese</a>, <a href="/zh_TW/">Traditional Chinese</a>, <a href="/id/">Bahasa Indonesia</a>, <a href="/de/">German</a>, <a href="/it/">Italian</a>, <a href="/cs/">Czech</a>, <a href="/bg/">Bulgarian</a> and <a href="/tr/">Turkish</a>.</p>
+
+{% if site.credits[page.lang] %}
+  <p>{{ site.credits[page.lang] }}</p>
+{% else %}
+  <p>{{ site.credits['en'] }}</p>
+{% endif %}