update readme to reference ch0.12.4
update readme to reference ch0.12.4

Reviewed-by: aruneshchandra
PR: #4

MetSystem/node-uwp,jianchun/node-uwp,Microsoft/node-uwp,munyirik/node-uwp,munyirik/node-uwp,jianchun/node-uwp,Microsoft/node-uwp,munyirik/node-uwp,MetSystem/node-uwp,Microsoft/node-uwp,MetSystem/node-uwp,jianchun/node-uwp