Optional config in OidcClient.

[magnushenning]

Alternative pull request to solve issue #5.

This allows for the developer to use:

var settings = { response_type: 'id_token token', ...};
var config = { responseType: 'text' };
var client = new OidcClient(settings, config);

I think this is a better solution than the other pull request. Let me know if you want any changes, e.g:

• maybe 'config' should be named 'options'
• maybe config.responseType should be config.httpRequest.responseType.

Magnus H.