GMC revives gas-guzzling Hummer as electric 'supertruck'

It may seem like an oxymoron that the massive, gas-guzzling GMC Hummer, once known as a symbol of overconsumption and excess, is back as a zero-emission, battery-powered electric car. 

But that's exactly what happened on Tuesday evening when the electrified Hummer was revealed through a video streamed on YouTube (you can...