Added @koenpunt to README

Author: koenpunt

README.md

@@ -24,5 +24,5 @@ We welcome all to participate in making Chosen the best software it can be. The
 
 - Concept and development by [Patrick Filler](http://patrickfiller.com) for [Harvest](http://getharvest.com/).
 - Design and CSS by [Matthew Lettini](http://matthewlettini.com/)
-- Repository maintained by [@pfiller](http://github.com/pfiller), [@kenearley](http://github.com/kenearley) and [@stof](http://github.com/stof).
+- Repository maintained by [@pfiller](http://github.com/pfiller), [@kenearley](http://github.com/kenearley), [@stof](http://github.com/stof) and [@koenpunt](http://github.com/koenpunt).
 - Chosen includes [contributions by many fine folks](https://github.com/harvesthq/chosen/contributors).