move widget shim to html.py

adding it in html.widgets removed the shim for top-level html

IPython/html.py

@@ -1,20 +1,24 b''
 """
 Shim to maintain backwards compatibility with old IPython.html imports.
 """
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 import sys
 from warnings import warn
 
 warn("The `IPython.html` package has been deprecated. "
-     "You should import from `jupyter_notebook` instead.")
+     "You should import from `jupyter_notebook` instead. "
+     "`IPython.html.widgets` has moved to `ipython_widgets`.")
 
 from IPython.utils.shimmodule import ShimModule
 
 sys.modules['IPython.html'] = ShimModule(
     src='IPython.html', mirror='jupyter_notebook')
 
+sys.modules['IPython.html.widgets'] = ShimModule(
+    src='IPython.html.widgets', mirror='ipython_widgets')
+
 if __name__ == '__main__':
     from jupyter_notebook import notebookapp as app
     app.launch_new_instance()