Fixing main code example in README.md

[mk53202]

Shouldn't the main code example be (device instead of led):

var blinkstick = require('blinkstick');

var device = blinkstick.findFirst();

device.blink('random', function(){
    device.pulse('random', function(){
        device.setColor('red', function(){
        });
    });
});

Let me know if I should do this as a pull request.

Mk...