For Windows 8 users... there is another option (maybe easier) to disable the signature check. From a CMD prompt, elevated with admin rights, type:
bcdedit -set loadoptions DISABLE_INTEGRITY_CHECKS
bcdedit -set TESTSIGNING ON
Reboot and you'll be able to install them. You'll still get prompted that the drivers are unsigned, so in my opinion, not completely unsafe... But if you want to re-enable, simply run these commands and reboot:
bcdedit -set loadoptions ENABLE_INTEGRITY_CHECKS
bcdedit -set TESTSIGNING OFF
Working on unlocking and rooting now... then waiting for a good ROM to show up.