Add df command

[i4ki]

@charlessachet Will you have time to finish this? Can I continue?

[charlessachet]

At that moment, no. I'm sorry...
And yes, you can go on and finish if you want :)

[]'s

[katcipis]

@charlessachet too busy having fun at Canada ? :-)

[charlessachet]

@katcipis I hope I start having fun in Canada soon :D
I'm sorry guys, I'd really like to help with the project and continue programming Golang.
Maybe in a few weeks! \o
[]'s