Currently, if you use axios with async / await, you get a stack trace like this:

```
Request failed with status code 500
    at createError (/Users/rmenezes/code/seedfi/web/node_modules/axios/lib/core/createError.js:16:15)
    at settle (/Users/rmenezes/code/seedfi/web/node_modules/axios/lib/core/settle.js:17:12)
    at IncomingMessage.handleStreamEnd (/Users/rmenezes/code/seedfi/web/node_modules/axios/lib/adapters/http.js:237:11)
    at IncomingMessage.emit (events.js:208:15)
    at IncomingMessage.EventEmitter.emit (domain.js:471:20)
    at endReadableNT (_stream_readable.js:1154:12)
    at processTicksAndRejections (internal/process/task_queues.js:77:11
```

It doesn't show you much about *what* called Axios., which makes debugging quite difficult!

This is because `settle` calls `createError`:
https://github.com/axios/axios/blob/master/lib/core/settle.js#L12-L24

Which creates a new error with a brand new stack trace:
https://github.com/axios/axios/blob/master/lib/core/createError.js#L15-L18

Perhaps we can fix this by creating an error before the request goes out and stitching it to the new error's stack trace?
test/unit/adapters/http.js
setTimeout(function () {
        assert.equal(success, false, 'request should not succeed');
        assert.equal(failure, true, 'request should fail');
        assert.equal(error.message, 'Unsupported protocol tel:');
        done();
      }, 300);
    })
  });
  it('should return unsupported protocol', function (done) {
    var success = false, failure = false;
    var error;
    server = http.createServer(function (req, res) {
      setTimeout(function () {
        res.end();
      }, 1000);
    }).listen(4444, function () {
      axios.get('ftp:google.com')
        .then(function (res) {
          success = true;
        }).catch(function (err) {
          error = err;
          failure = true;
        })
      setTimeout(function () {
        assert.equal(success, false, 'request should not succeed');
        assert.equal(failure, true, 'request should fail');
        assert.equal(error.message, 'Unsupported protocol ftp:');
        done();
      }, 300);
    })