Two fixes: for a bug in Stripe multiple charges and support for more Balanced parameters

This fork fixes two issues in ActiveMerchant v1.34.0:

1. The Stripe gateway was unable to handle secondary charges on an existing customer token.  The bug was that it left out the customer token in the call to Stripe's API service.

2. The Balanced gateway did not fully support the :on_behalf_of_uri parameter, and it did not have any support for the :appears_on_statement_as or :meta parameters.  This fork adds such support.