Auto merge of #272 - QuintenJohnson:fix/installation-warning-messages, r=fmoko
Auto merge of #272 - QuintenJohnson:fix/installation-warning-messages, r=fmoko

fix(installation): make fatal errors more obvious

I initially ran the installation script without rust installed. The fact that the error message was labeled with WARNING made me unsure whether installation was successful or I needed to re-run after installing rust. There's an error code returned on fatal errors, but this change will make things clearer.

carols10cents/rustlings,carols10cents/rustlings