Throw a specific error when wifi is not actived

[Emmanuel Haguet]

1/ On Mac, disable wifi
2/ run the example of README

The error return :
(node:27211) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): Error: Could not get SSID

expectation : return a specific error (Error: Wifi disabled. Can get SSID.)

[Kevin Mårtensson]

Thanks for reporting. I've published a new release with a fix.