Change tagline

The previous one didn’t communicate that this is a thing for sending
stuff to your users. The lede already explains that it’s a thing for
government.

app/templates/views/signedout.html

@@ -15,11 +15,11 @@
       <div class="grid-row">
         <div class="column-two-thirds">
           <h1>
-            Email and text messaging for government services
+            Send emails and text messages to your users
           </h1>
           <p>
             If you work for a UK government department or agency you can
-            try GOV.UK Notify now
+            try GOV.UK Notify now.
           </p>
           <div class="button-container">
             <a class="button button-start" href='{{ url_for('.register' )}}'>