paypal: create BAID for payment method

A BAID is generated when adding a payment method and used to charge the
account in Paypal.

Signed-off-by: Pierre-Alexandre Meyer <pierre@ning.com>
travis: add ruby tests

Signed-off-by: Pierre-Alexandre Meyer <pierre@ning.com>
killbill: update to latest version (1.0.9)

Signed-off-by: Pierre-Alexandre Meyer <pierre@ning.com>