Improve runNodeTest() so that it works similarly to runSVGTest(). runNodeTest() now tests all three fonts, and outputs images files with names like:
Improve runNodeTest() so that it works similarly to runSVGTest().
runNodeTest() now tests all three fonts, and outputs images files
with names like:

  Accidental.Basic.Bravura.png
  Accidental.Basic.Gonville.png
  Accidental.Basic.Petaluma.png
  Vibrato.Harsh_Vibrato.Bravura.png
  Vibrato.Harsh_Vibrato.Gonville.png
  Vibrato.Harsh_Vibrato.Petaluma.png

Tails/vexflow,Tails/vexflow,Tails/vexflow