uppAliasOnly is deprecated; use useAlias

See issue #5

This should have no noticeable change to functionality and requires no change of use.

There may be a subtle change to the way the gateway works. Previously, fetching a card alias only (by setting a zero amount) did not fully authenticate the card; it only validated the card. This was not fully clear in the documentation, but it meant a card that had a valid lunn check always came back as a successful fetch of a cardReference, whether the card was really valid or not. This would only be discovered at the back-end "repeat payment" use of that card alias. The older uppAliasOnly flag has been deprecated for a while and appears to be disappearing from the documentation now.

The new method will authenticate the card too, using whatever method the gateway uses (often done by authorising a small amount then instantly cancelling it). This allows the merchant site to catch an invalid card a little earlier in the repeat payment process.