Show a tour when users first create a service

This commit adds a 3 screen tour, similar to those used on GOV.UK Verify
and Passports.

We guerilla tested this on Friday, and it really helped users to build a
mental model of how Notify works, so that when they’re playing around
with it they have a greater sense of what they’re aiming to do. This
makes concepts like templates and placeholders click more quickly.

https://www.pivotaltracker.com/story/show/116710119

app/main/views/add_service.py

@@ -44,7 +44,7 @@ def add_service():
                                                        user_id=session['user_id'],
                                                        email_from=email_from)
 
-        return redirect(url_for('main.service_dashboard', service_id=service_id))
+        return redirect(url_for('main.tour', service_id=service_id, page=1))
     else:
         return render_template(
             'views/add-service.html',