Debounce using GCD?

[onmyway133]

Hi Jens,

Just a suggestion, how about refactoring debounce to GCD source, so that we can schedule and cancel when needed, like https://github.com/onmyway133/Signal/blob/master/Pod/Classes/Signal%2BDebounce.swift and http://mokagio.github.io/tech-journal/2014/11/18/objective-c-throttling-with-gcd.html

[JensRavens]

Thanks for the reference. This would definitely an improvement.