Remove the "HTTP/1.0 200 Connection established" string from the response when going through a proxy using cURL.

First of all, thanks for the great library! At my company, when using cURL, we always need to go through a proxy. The problem is that when a request goes through a proxy, the first line of the response always includes:

`HTTP/1.0 200 Connection established`

The `parseResponse` function in `Response.php` does not facilitate this scenario. If this string is included in the response, the response is not correctly parsed. I.e. when trying to read the the HTTP response code, the function will always return the `200` response code for every response.

An example:

A typical 404 response when we go through a proxy:

```
HTTP/1.0 200 Connection established

HTTP/1.1 404 Not Found
Server: Apache-Coyote/1.1
Pragma: no-cache
Cache-Control: no-cache
Expires: Thu, 01 Jan 1970 00:00:00 GMT
Cache-Control: no-store
Content-Length: 13
Date: Wed, 13 Feb 2013 16:36:43 GMT
```

The response function will always return the `200` code instead of the correct `404` code (which is what we want)

If you agree with the change, please could you push it. Thank you.