BF Get textstim_vs_textbox demo running again

As reported by @alexholcombe here: https://discourse.psychopy.org/t/textstim-vs-textbox-py-demo-not-working/2055 this demo had stopped working. Seems to be resolved by explicitly importing the textbox class. 
Perhaps there is a cleaner way to fix this?

Author: m-macaskill

psychopy/demos/coder/stimuli/textBoxStim/textstim_vs_textbox.py

@@ -19,6 +19,7 @@
 import string
 import random
 from psychopy import visual, core, event
+from psychopy.visual import textbox
 from psychopy.iohub.util import NumPyRingBuffer
 import pyglet.gl as gl
 
@@ -81,7 +82,7 @@ def updateStimText(stim,text=None):
                         )
 
 # Find a font that is available on the system.
-fm=visual.textbox.getFontManager()
+fm = textbox.getFontManager()
 available_font_names=fm.getFontFamilyStyles()
 prefered_fonts=[fn for fn,fs in available_font_names if fn in [
                                                             'Courier New',
@@ -218,4 +219,4 @@ def updateStimText(stim,text=None):
     print
     print '---------------------------------------'
 
-core.quit()
+core.quit()