add end to end test for actual integration testing

requires env variables:

    FIXFLO_USERNAME
    FIXFLO_PASSWORD
    FIXFLO_CUSTOM_DOMAIN
    FIXFLO_3RD_PARTY_USERNAME
    FIXFLO_3RD_PARTY_PASSWORD

still working out some of the correct process to interact with the
api - have added url_suffix so can direct at test server if required