Bring main callback to node.js error conventions

[RomanMinkin]

Bring main callback to node.js error conventions instead of having both error and response data in one variable, because actual response is not an error. http://docs.nodejitsu.com/articles/errors/what-are-the-error-conventions

So the actual call would look like

sms.sms_send({
  to: '79112223344',
  text: 'Текст SMS'
}, function(error, response) {
    console.log(error, response))
})

[Borodin]

@RomanMinkin, thanks, I corrected.