get rid of revese dependencies in textcell

notebook/static/base/js/namespace.js

@@ -51,6 +51,9 @@ define(function(){
     jglobal('Session','services/sessions/session');
     jglobal('LoginWidget','auth/js/loginwidget');
     jglobal('Page','base/js/page');
+    jglobal('TextCell','base/js/textcell');
+    jglobal('MarkdownCell','base/js/textcell');
+    jglobal('RawCell','base/js/textcell');
 
     Jupyter.version = "4.0.0.dev";
     Jupyter._target = '_blank';

notebook/static/notebook/js/textcell.js

@@ -2,7 +2,6 @@
 // Distributed under the terms of the Modified BSD License.
 
 define([
-    'base/js/namespace',
     'base/js/utils',
     'jquery',
     'notebook/js/cell',
@@ -14,7 +13,7 @@ define([
     'codemirror/lib/codemirror',
     'codemirror/mode/gfm/gfm',
     'notebook/js/codemirror-ipythongfm'
-], function(IPython,
+], function(
     utils,
     $,
     cell,
@@ -360,11 +359,6 @@ define([
         return cont;
     };
 
-    // Backwards compatability.
-    IPython.TextCell = TextCell;
-    IPython.MarkdownCell = MarkdownCell;
-    IPython.RawCell = RawCell;
-
     var textcell = {
         TextCell: TextCell,
         MarkdownCell: MarkdownCell,