minor changements
Modified parsing of authorization request. Each value that is not properly formatted is set to Void. TODO: Finish this.
Modified 'compute_expected_response' feature. Added support for qop not being present (for compatibility with RFC 2069). TODO: Test this.
bug fixes
get_header_value_by_key not returns Void, if key not found in header. This is to support our design model: If a value has not the expected format, it is set to Void.
Minor changes.