Brandur 1ca67cb954 Correct behavior for error logging
A few changes:

* Add a new `Util.log_error` method which will forward to the equivalent
  of `#error` on a logger.
* Move errors produced by `StripeClient` to use `Util.log_error`.
* Change standard stdout logging behavior to log to stderr in the case
  of `Util.log_error.
* Change `Stripe.log_level` values to be an enum in a similar fashion as
  the standard library's built in `Logger`.
2017-08-11 11:45:43 -07:00
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2017-08-11 11:45:43 -07:00