Requests with invalid credentials should terminate with a 401 code

As defined in RFC 7235 https://tools.ietf.org/html/rfc7235#section-3.1

Fixes #1159

Fixed redirect with completion property not being called

These are currently failing

Stream Usage

Adding the possibility to receive the callback to a different queue for all responses

Fixed unmatching Serializer with testThatJSONResponseSerializerSucceedsWhenDataIsValidJSON

Feature - Override Closures with Completion

Adding the possibility to receive the callback to a thread different from the main one to all response methods.

- stringResponseSerializer on Testing JSONResponseSerializer