如何在我的codeigniter项目中安装github源代码

I need to use this: https://github.com/bdelespierre/php-kmeans in my codeigniter project, however composer shows this:

bdelespierre/php-kmeans 1.0 exists as bdelespierre/php-kmeans[dev-master] but these are rejected by your constraint.

Any idea what I do wrong?