Auto merge of #3570 - integer32llc:fix-slug-link, r=alexcrichton
Auto merge of #3570 - integer32llc:fix-slug-link, r=alexcrichton

Link to the category slugs page from the docs instead

Oops, just noticed that I didn't change this link in the docs when we changed to specifying slugs for categories in `Cargo.toml` :-/

rustyhorde/cargo,vojtechkral/cargo,eminence/cargo,durka/cargo,tshepang/cargo,tsurai/cargo,sbeckeriv/cargo,tsurai/cargo,nipunn1313/cargo,rustyhorde/cargo,nipunn1313/cargo,achanda/cargo,eminence/cargo,achanda/cargo,durka/cargo,tsurai/cargo,tsurai/cargo,eminence/cargo,durka/cargo,rust-lang/cargo,rustyhorde/cargo,vojtechkral/cargo,durka/cargo,sbeckeriv/cargo,rustyhorde/cargo,tsurai/cargo,eminence/cargo,tshepang/cargo,tshepang/cargo,sbeckeriv/cargo,vojtechkral/cargo,rust-lang/cargo,nipunn1313/cargo,achanda/cargo,achanda/cargo,tshepang/cargo,rust-lang/cargo,rust-lang/cargo,sbeckeriv/cargo,vojtechkral/cargo,nipunn1313/cargo