Embrace flexible box model
Added baseline and stretch
Renamed *Widget to *,
depracted old names.
Fix interact tests for rename
adding hbox and vbox

Conflicts:
	IPython/html/static/widgets/js/widget_container.js
	IPython/html/widgets/widget_container.py
Make HBox and VBox helper functions
Added some doc strings on the widgets.
Also address the comments Matthias left me.
Added incompat for name deprecation.
Rebase cleanup
s/Container/Box
Added comment about box rename.
Filenames s/container/box
Address Sylvain's comments.
Fab CSS
Make popup inherit from widget box
Fix logic, use box where applicable
	renamed:    widget_container.js -> widget_box.js
Fixed typo
Fix typo in deprecated class name.
s/that/this bug