Make Help accessible for guests.

app/controllers/help_controller.rb

 class HelpController < ApplicationController
+  skip_before_action :authenticate_user!, :reject_blocked
+
   layout 'help'
   def index

app/views/help/show.html.haml

 - page_title @file.humanize, *@category.split("/").reverse.map(&:humanize)
 .documentation.wiki
-  = markdown @markdown.gsub('$your_email', current_user.email)
+  = markdown @markdown.gsub('$your_email', current_user.try(:email) || "email@example.com")