Update GRAINS image and/or text

[eclab]

The image used for GRAINS is the old module without the M/G switch. Either:

• Replace the image with a new image showing the M/G switch, OR

• Replace the "GRAINS has had two versions" paragraph with:

  GRAINS has had two versions. The original version (shown in the image above) was primarily programmed using Ginkosynthese's original software library. The new version can also be programmed using the Mozzi Library. These libraries use different pins on the ATmega 328P chip to output sound: so the new version includes a switch ("M/G") to select which pin to use.