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/templates/views/tour/4.html

@@ -0,0 +1,28 @@
+{% extends "withoutnav_template.html" %}
+{% from "components/textbox.html" import textbox %}
+{% from "components/page-footer.html" import page_footer %}
+{% from "components/banner.html" import banner_wrapper %}
+
+{% block page_title %}
+  {{heading}} – GOV.UK Notify
+{% endblock %}
+
+{% block maincolumn_content %}
+
+  {% call banner_wrapper(type='tour') %}
+	<h2 class="heading-large">Send your messages</h2>
+	<p>
+		Notify merges your data with the template and sends the messages
+	</p>
+	<a href="{{ url_for('.service_dashboard', service_id=service_id) }}">
+      Next
+    </a>
+	<img
+		src="/static/images/tour/{{ current_page }}.png"
+		class="banner-tour-image-flush-bottom"
+		width="840" height="290"
+		alt="Three mobiles phones, each showing a text message personalised with data about the recipient"
+	>
+  {% endcall %}
+
+{% endblock %}