Cheat sheets about installation for the workshop

[milibopp]

People might show up to a workshop with an unprepared computer. @broesamle and I think it would be helpful to have a cheat sheet for all major operating systems to give people a guideline how to setup a Rust development environment on their computer.

[booyaa]

Is this not a similar aim? #18

Here's what's been written so far: https://github.com/rust-community/rustbridge/blob/master/workshops/installfest/user-guide.md

[broesamle]

we see it (almost) as part of or as result of #18

its more about the format: each OS gets its own cheat sheet with easy to use newbee instructions.