updated install.sh for linux users. catches git not being installed
updated install.sh for linux users. catches git not being installed

sebastienvercammen/ptc-acc-gen,FrostTheFox/ptc-acc-gen,FrostTheFox/ptc-acc-gen,sebastienvercammen/ptc-acc-gen,FrostTheFox/ptc-acc-gen,sebastienvercammen/ptc-acc-gen