How can I disable kext signing in Mac OS X 10.10 Yosemite?
To disable the kext signing security setting:

sudo nvram boot-args=kext-dev-mode=1


After changing this setting you need to restart the computer to have OS X recognize it.

It is important to note that the kext-signing setting is global, if you disable it you should be careful to only install system drivers from sources that you trust.

To reenable again use:

sudo nvram -d boot-args