New features and improvements:

• When an error occurs and there is a related Throwable object, pass it to the onError hook handlers. (#46)
• When forceRefresh fails and there is a related Throwable object, expose it in RefreshResult via the new getErrorException property.
• Handle unexpected errors in the forceRefresh method (to stop potential unhandled exceptions thrown by the evaluation logic from bringing down the consumer's application).

Breaking changes:

• Rename the getError property to getErrorMessage in RefreshResult. (Low impact expected.)
• Add an extra parameter of type ?Throwable to the onError hook handlers. (Low impact expected.)
• Don't include event_id in the log message but leave it up to the actual logger implementation to choose the log message format. (Affects consumers using custom logging only.)