Users can't upgrade the firmware if jade repo directory exists

[epiccurious]

The script is designed to pull the most recent Jade changes only if the ~/jade directory doesn't exist.

This was intentional to prevent having to clone the repo again every runtime.

It also allows users to clone and customize their Jade firmware before running the script.

As a workaround, users who are trying to upgrade their DIY Jades to 1.0.21 from 0.47 or 0.48 can run the following in Terminal:
rm -rf ~/jade

Then re-run the script.

Need to figure out a better solution, such as perhaps prompting the user to overwrite the directory.