Bitstamp Fixes From Auth Demo Testing

Finally remembered to go test out the authenticated methods for bitstamp.... I think we should encourage anyone doing changes to these calls to get a verified account for that exchange.  The getDepositAddress was returning a boolean as the result.  I also added error handling for canceling orders.  All the other auth methods are working.

I was in a rush to fix this when I noticed it and I forgot to switch from my current develop branch, so it also includes the raw implementation for Coinbase.  Its useful in its current state for all of the non authenticated calls.  I can spend some time separating them out, but I figured it would be better to get this fix in.