While GO offers the ability to recover from panic there is no way to intercept an os.Exit event. To allow graceful shutdown and clean-up or programs which use Logrus to Fatal out I've borrowed ideas from the `atexit` package and enhanced Logrus.
Usage:
* When setting up the logger one call `RegisterExitHandler( func() {...} )` to add a handler that will be invoked for any `Fatal` call to the logger.