API Version 2.0.9 + PHP7 Compatibility Fix

Updated to use the latest version of the WSDL and endpoint as specified at https://developer.royalmail.net/node/688#/

Fixed array referencing issue that was stopping it working with the version of SoapClient in PHP 7+

Updated auth headers.

Updated auth from @minioak to work with Royal Mail onboarding.

First Alpha minus typo in test.

v0.1.0.1

typo