Thread model and UI improvements

Adds thread model/collection for managing conversation-level state, such
as unreadCounts, group membership, thread order, etc... plus various UI
improvements enabled by thread model, including an improved compose
flow, and thread-destroy button.

Adds Whisper.notify for presenting messages to the user in an orderly
fashion. Currently using a growl-style fade in/out effect.

Also some housekeeping:
Cut up views into separate files.
Partial fix for formatTimestamp.
Tweaked buttons and other styles.

js/views/notifications.js

@@ -0,0 +1,34 @@
+var Whisper = Whisper || {};
+(function () {
+  'use strict';
+
+  // This is an ephemeral collection of global notification messages to be
+  // presented in some nice way to the user. In this case they will fade in/out
+  // one at a time.
+
+  var queue = new Backbone.Collection();
+  var view  = new (Backbone.View.extend({
+    className: 'help',
+    initialize: function() {
+      this.$el.appendTo($('body'));
+      this.listenToOnce(queue, 'add', this.presentNext);
+    },
+    presentNext: function() {
+      var next = queue.shift();
+      if (next) {
+        this.$el.text(next.get('message')).fadeIn(this.setFadeOut.bind(this));
+      } else {
+        this.listenToOnce(queue, 'add', this.presentNext);
+      }
+    },
+    setFadeOut: function() {
+      setTimeout(this.fadeOut.bind(this), 1500);
+    },
+    fadeOut: function() {
+      this.$el.fadeOut(this.presentNext.bind(this));
+    },
+  }))();
+
+  Whisper.notify = function(str) { queue.add({message: str}); }
+
+})();