Add payment term day to gmo konibin post paramter.

As GMO specification, When the options has not the payment term day key, it
uses the value set in the account GMO.

So, If the options has not payment term day, it does not include the post
parameter.
Merge pull request #3 from miyazawadegica/gmo_cents

Add payment term day to gmo konibin post paramter.