Update README.md

Adding new command for ftdi_sio which applies to Kernel>3.12 used by Ubuntu 14.04 LTS
Adding a CONTRIBUTING file to use github feature

https://github.com/blog/1184-contributing-guidelines
Merge pull request #746 from sieben/contributing

Adding a CONTRIBUTING.md file to use a nice github feature
Merge pull request #732 from camilorodegheri/patch-1

Update README.md
Merge commit '95e2cd9021110609d6a067ce5067aee0bbdc6336' into HEAD