Install script should check for (armv6l || armv7l) to support Raspberry Pi 1 and 2

[jvolker]

As mentioned in OpenframeProject/Openframe#81 (comment)

I found the issue: Processing wasn't installed because the 2B's architecture is armv6l. I must have missed the error message during the extension installation.

To fix this, installed Processing by following the instructions at https://pi.processing.org/download/:

curl https://processing.org/download/install-arm.sh | sudo sh