update readme with new preferred Singularize/Pluralize API
update readme with new preferred Singularize/Pluralize API

mrchief/Humanizer,ErikSchierboom/Humanizer,HalidCisse/Humanizer,jaxx-rep/Humanizer,schalpat/Humanizer,HalidCisse/Humanizer,HalidCisse/Humanizer,aloisdg/Humanizer,MehdiK/Humanizer,schalpat/Humanizer,Flatlineato/Humanizer,mrchief/Humanizer,Flatlineato/Humanizer,ErikSchierboom/Humanizer,mrchief/Humanizer,hazzik/Humanizer