Merge branch 'master' into sliders
Add new sliders. Subtract old sliders. Show two strings.
Any strings that are not the current string go gray. The goal string
now plays the correct frequency and displays the correct length/width.
I added some more text with instructions that are displayed.

Right now, these instructions say that you can use the sliders to
adjust String 2. They should say something like “Use the sliders to
change the properties of the current string.” and then display which is
the current string.
Merge branch 'sliders'

Conflicts:
	StringPrototype_v4/StringPrototype_v4.pde