Add support for JCB and Diners Club cards.

According to the [documentation](https://support.balancedpayments.com/hc/en-us/articles/200319895-Does-Balanced-accept-JCB-and-Diners-Club-cards) Balanced supports JCB and Diners, but they weren't recognized by balanced-js. I added support for their prefixes based on Wikipedia. Also added test card numbers found elsewhere online; these should be changed if there are specific numbers you support.

-Zach