Allow From Anywhere (Disable Gatekeeper checks) in macOS

Apple has removed the option to Allow apps downloaded from Anywhere in macOS Sierra. To enable this, use /Applications/Utilities/Terminal. Note, if you had Allow from Anywhere enabled in OS X El Capitan it will persist upon Sierra update.

Allow from Anywhere (Turns off the Gatekeeper checks)

sudo spctl --master-disable

Re-enable:

sudo spctl --master-enable