Auto merge of #206 - ajaxm:ajaxm/rustup-update, r=komaeda

Suggest rustup update in readme

I'm pretty new to Rust. I tried installing rustlings for the first time and got this error:
```
$> cargo install --force --path .
error: `/Users/ajax/projects/rust/rustlings` is not a crate root; specify a crate to install from crates.io, or use --path or --git to specify an alternate source

Caused by:
  failed to parse manifest at `/Users/ajax/projects/rust/rustlings/Cargo.toml`

Caused by:
  editions are unstable

Caused by:
  feature `edition` is required

this Cargo does not support nightly features, but if you
switch to nightly channel you can add
`cargo-features = ["edition"]` to enable this feature
```

I'm not sure if the answer was to run `rustup update` but I noticed that I was running Rust 1.29.0, so updated to 1.36.0 and got it working. If there's a way to specify a minimum required version, pls let me know.

Lastly, the whitespace changes were automatic from my editor. What's the convention here for making such updates? Thanks!

0 files changed, 0 insertions, 0 deletions