Add instructions on how to run apollo-miner as non-privileged user

[golden-guy]

@jstefanop As a suggestion, you should really update the README on how to run the miner as non-root user:

On most linux distros all that's needed is to add the respective user to the dialout group (since that group has rw perms on /dev/ttyACM0)

sudo usermod -aG dialout <user>

Re-login or reboot for the changes to take effect.

[github12101]

+1 totally agree.