[#1875] - Added error code for customer id is required.
[#1875] - Added error code for customer id is required.

braintree/braintree_dotnet,ronin1/braintree_dotnet,scottmeyer/braintree_dotnet,scottmeyer/braintree_dotnet,ronin1/braintree_dotnet,braintree/braintree_dotnet,ronin1/braintree_dotnet,scottmeyer/braintree_dotnet,scottmeyer/braintree_dotnet