Add refund list to charge object

I've added Refunds to the Charge.  

In June Stripe changed the format of the refunds property (https://stripe.com/docs/upgrades#2014-06-17) so I thought I might as well do the new version rather than the old one.

Note the following:
 
* not sure if they're using it anywhere else already but it seems likely they'll use the "list container" pattern again so I created StripeDataList<T>.  You may wish to do something clever with the URL property on here.  There again you may not.

* the other breaking change that affected me was renaming type to brand on the card object.  Hence I've updated this

* there may be other breaking changes.  A lot of the tests failed but a lot of this was because I'm in the UK so transfers for example are not possible here.  Hence this PR is probably not totally ready-to-go but will hopefully give you a bunk up at some point.

Thanks.  And thanks for maintaining this library.

G