incorrect display of unpitched notes

[GoogleCodeExporter]

Hi, 

Firstly, I would like to say I love what you've got done with the program, so 
far.
I am currently working on a smaller scale musicxml parser with the use of 
vexflow, however, I would say that your program is already exceeding that of 
vexflow. 
Before I continue there are a couple more things I have come across, but I will 
put them in separate issues for you.

When using a musicxml document that uses percussion, the xml uses:
note > unpitched > display step
instead of note > pitch > step

This is causing all notes to be displayed as a B on the stave.

Ross

Original issue reported on code.google.com by [email protected] on 23 Sep 2012 at 6:38