Remove unnecessary fat arrows
Fix bug in $.payment.formatCardNumber
Fix bug where AMEX receives extra spaces
Fix `input` event support

Some mobile devices only emit an `input` event, and others will emit both
`input` and `key*` events. This change addresses both cases:

* For those that only support `input`, the `reFormat*` functions will
  update the element with the proper value on the next tick.
* For those that support both, the `key*` defaults will be prevented and
  the element will be updated with the proper value on the next tick.
  Attempting to do both in the same tick results in incorrect cursor
  positioning.
Update tests to be asynchronous
Add test for AMEX space issue
Fix backspacing issue on expiry inputs
Update build output
Merge pull request #102 from stripe/stripe-integrate

Integrate changes from Stripe Checkout