Fix show by calling vplot() instead of plot(VBox).
Fix show by calling vplot() instead of plot(VBox).

Bokeh has changed the import location of VBox. We could still use it, but the
favored API now seems to be vplot.

Plourde-Research-Lab/PyQLab,rmcgurrin/PyQLab,BBN-Q/PyQLab,calebjordan/PyQLab