process superagent response to get better error logging result

Example

````
const request = require(‘superagent’);
const serial = require(‘util-superagent-serializer’);

superagent.get(restful_url)
.end((err, res)=>{

// superagent will detect general http level error for you(404, 403, 500...)
if (err) return console.error(err);
// Golden Rule: in javascript, you should trust your own input
// But, you should NEVER trust 3rd party input. `res` is 3rd party input
if (!isSomething(res)) return console.error(NotSomethingErr(res));
// Now, you can trust the res, and continue your codes
....

});

function isSomething(res) {
// check if the res is something you want here
}

function NotSomethingErr(res) {

var err = new TypeError(‘we got something unknown’);

// serialize the res, and log the error, so we know what happened.
err.original = serial(res);
return err;
}