Bumblebee version 2.1

This version of Bumblebee fixes some errors that happened quite often with the previous versions (USB data overflow), and is only compatible for the moment with the author's Killerbee fork (https://github.com/virtualabs/killerbee).

This version has been heavily tested and does not seem to produce this USB data overflow error anymore. Feel free to register an issue if you experience some trouble using this version !