Got "API rate limit exceeded" from github upon first command

[noamraph]

Hi, I started following the tutorial (in a new docker container), and got this:

root@0d2a208adf95:/# echo "Hello Nix" | nix run "nixpkgs#ponysay"
error:
       … while fetching the input 'github:NixOS/nixpkgs/nixpkgs-unstable'

       error: unable to download 'https://api.github.com/repos/NixOS/nixpkgs/commits/nixpkgs-unstable': HTTP error 403

       response body:

       {"message":"API rate limit exceeded for <IP REMOVED>. (But here's the good news: Authenticated requests get a higher rate limit. Check out the documentation for more details.)","documentation_url":"https://docs.github.com/rest/overview/resources-in-the-rest-api#rate-limiting"}

It may be because I'm trying this from work, and there are a lot of users behind this IP address.

I suggest to add a link to an instruction page saying what to do?

[lucperkins]

Fixed by #350