Add redirect_from plugin

Redirect /merlin6 to introduction

_config.yml

@@ -56,6 +56,12 @@ feedback_email: merlin-admins@lists.psi.ch
 # feedback_link: "http://helpy.io/"
 # if you uncomment the previous line, it changes where the feedback link points to
 
+plugins:
+  - jekyll-redirect-from
+
+whitelist:
+  - jekyll-redirect-from
+
 highlighter: rouge
 # library used for syntax highlighting