Feature Request: Allow to filter out specific hostnames when capturing HTTP(s) requests

## Description

As a user I would like to be able to filter out from my traces specific requests based on the hostname of the request itself when using `captureHTTPsGlobal` & `captureHTTPs`. This way I can avoid sending sensitive data or polluting traces to X-Ray when I instrument my functions.

## Example

```javascript
var AWSXRay = require('aws-xray-sdk');
AWSXRay.captureHTTPsGlobal(require('http'));
var http = require('http');

// ignore requests to test.myapp.com
AWSXRay.ignore_hostnames('test.myapp.com');
// OR ignore requests to test.myapp.com AND other.myapp.com
AWSXRay.ignore_hostnames(['test.myapp.com', 'other.myapp.com']);
```

`aws-xray-sdk-python` supports this: https://github.com/aws/aws-xray-sdk-python#ignoring-httplib-requests