Restyle compose button

Move it to a tool bar at the top of the conversation list. This is also
where a search bar will live someday.

Fixes #357

// FREEBIE

js/views/inbox_view.js

@@ -108,7 +108,7 @@
                 'click': 'closeMenu',
                 'click .hamburger': 'toggleMenu',
                 'click .show-debug-log': 'showDebugLog',
-                'click .fab': 'showCompose',
+                'click .show-new-conversation': 'showCompose',
                 'select .gutter .contact': 'openConversation'
             },
             openConversation: function(e, data) {