fix contributing guide in README.md
fix contributing guide in README.md
matham/kivy,kivy/kivy,inclement/kivy,akshayaurora/kivy,matham/kivy,rnixx/kivy,matham/kivy,akshayaurora/kivy,kivy/kivy,rnixx/kivy,akshayaurora/kivy,matham/kivy,rnixx/kivy,inclement/kivy,inclement/kivy,kivy/kivy