Confirmaton on send, banner when 'unverified'

Not yet using the new APIs, but ready to. Still to do:
- Send sync messages on trust decisions
- Respond to received trust decision sync messages
- Show trust decisions in the conversation history
- In that rare situation where a sent message ends up with a key error
  make it easy to retry the send.

FREEBIE

js/views/banner_view.js

@@ -0,0 +1,36 @@
+/*
+ * vim: ts=4:sw=4:expandtab
+ */
+(function () {
+    'use strict';
+    window.Whisper = window.Whisper || {};
+
+    Whisper.BannerView = Whisper.View.extend({
+        className: 'banner',
+        templateName: 'banner',
+        events: {
+            'click .dismiss': 'onDismiss',
+            'click .body': 'onClick',
+        },
+        initialize: function(options) {
+            this.message = options.message;
+            this.callbacks = {
+                onDismiss: options.onDismiss,
+                onClick: options.onClick
+            };
+            this.render();
+        },
+        render_attributes: function() {
+            return {
+                message: this.message
+            };
+        },
+        onDismiss: function(e) {
+            this.callbacks.onDismiss();
+            e.stopPropagation();
+        },
+        onClick: function() {
+            this.callbacks.onClick();
+        }
+    });
+})();