subscription: Improve email-hint popover style.

static/styles/subscriptions.css

@@ -10,10 +10,15 @@
     margin: 0;
 }
 
+.email_address_hint {
+    max-width: 430px;
+    padding-left: 10px;
+    padding-right: 10px;
+}
+
 .subscription-email-hint-image {
     float: right;
     width: 80px;
-    padding-right: 60px;
 }
 
 .subscription_header.collapsed {

static/templates/email_address_hint.handlebars

@@ -1,14 +1,10 @@
 {{! Explanation of the stream email address }}
-<div>
-
+<div class="email_address_hint">
     <p>{{#tr this}}You can send emails to Zulip! Just copy and use this address as an email recipient, and:{{/tr}}</p>
-
     <img class="subscription-email-hint-image" src="/static/images/integrations/zulip_mail.png" />
-
     <ul>
         <li>{{t "The email will be forwarded to this stream" }}</li>
         <li>{{#tr this}}The email subject will become the Zulip topic{{/tr}}</li>
         <li>{{#tr this}}The email body will become the Zulip message{{/tr}}</li>
     </ul>
-
 </div>