Add John Ivison to Contributors list

Created by: jivison

Contributors.md

@@ -113,6 +113,7 @@ Edison Shek
 - [Mathilde Pind] (https://github.com/mathildepind)
 - [Massimo7](https://github.com/Massimo7)
 - [Sergio Abreu García](https://github.com/saggamedeveloper)
+- [John Ivison](https://github.com/mattecatte)
 - [Zeddmaxx](https://github.com/zeddmaxx)
 - [Anupama Garani](https://github.com/anusky95)
 - [Lee T](https://github.com/leeturnbill)