Added curlOptions to config. Object curlOptions will be passed to curl as options.

I need to change the encoding in curl.

No I can do something like this, if I get the wrong encoding:
```
var config = {
    url: 'http://somesite.org',
    curlOptions: {
        encoding: null,
        process: function(body) {
            var iconv = new Iconv('ISO-8859-1', 'UTF-8');
            return iconv.convert(body).toString();
        }
    },
    ...
```