Change start button text for benchmarking

This commit changes the start button text for the benchmarking
exercise, due to start on the 24th.

A helper (start_button) is defined that caters for the change of the
start button text.

The following smarts-answer (and button text) are affect by this commit:

- Overseas passport => "Continue"
-  calculate-your-child-maintenance => "Calculate your child maintenance"

app/helpers/application_helper.rb

@@ -10,4 +10,15 @@ def ajax_enabled_for?(name)
       register-a-death
     ).exclude?(name)
   end
+
+  def start_button
+    case @name.to_s
+    when "overseas-passports"
+      "Continue"
+    when "calculate-your-child-maintenance"
+      "Calculate your child maintenance"
+    else
+      "Start now"
+    end
+  end
 end

app/views/smart_answers/_landing.html.erb

@@ -18,7 +18,7 @@
       <div class="intro">
         <%= start_node.body %>
         <p class="get-started">
-          <a rel="nofollow" href="<%= smart_answer_path(@name, started: 'y') %>" class="big button">Start now</a>
+          <a rel="nofollow" href="<%= smart_answer_path(@name, started: 'y') %>" class="big button"><%= start_button %></a>
         </p>
       </div>
       <%= start_node.post_body %>