move iframe creation into Browser

src/browser.coffee

@@ -1,4 +1,13 @@
+$ = require 'jquery'
+
 module.exports =
 class Browser
   constructor: (@path) ->
-  on: ->
+    $('.main.pane').append @html().hide()
+  on: ->
+  html: ->
+    $ "<iframe src='#{@path}' style='width:100%;height:100%'></iframe>"
+  show: ->
+    $(".main iframe[src='#{@path}']").show()
+  hide: ->
+    $(".main iframe[src='#{@path}']").hide()

src/editor.coffee

@@ -162,12 +162,7 @@ class Editor
       @ace.setSession buffer
     else
       $('#ace-editor').hide()
-      path = buffer.path
-      if $("iframe[src='#{path}']").length
-        $("iframe[src='#{path}']").show()
-      else
-        $('#ace-editor').after iframe =
-          "<iframe src='#{path}' style='width:100%;height:100%'></iframe>"
+      buffer.show()
 
     Storage.set @focusedPathKey, path
     Event.trigger "editor:bufferFocus", path