Basic auth not working for multiple requests

[ahansson89]

[ramesh-tr]

Related - #242

[shadyvb]

This is caused by the Requests_Auth_Basic::register method only hooking into curl.before_send and not curl.before_multi_add ( the first is not called by request_multiple ).

refs:

https://github.com/rmccue/Requests/blob/master/library/Requests/Auth/Basic.php#L56

https://github.com/rmccue/Requests/blob/master/library/Requests/Transport/cURL.php#L208

So we have either of two solutions, and I'm unsure which is best:

1. Call curl.before_send within Requests_Transport_cURL::request_multiple
2. Register a hook to curl.before_multi_add in Requests_Auth_Basic::register