Find way to make obvious what all extension methods exist in the docs

[epage]

Right now you have to hunt through all of the traits and it makes it hard to see the big picture.

[killercup]

All hail @QuietMisdreavus, almighty solver of docs problems:
https://twitter.com/QuietMisdreavus/status/1023416134903783429

[QuietMisdreavus]

Thank @GuillaumeGomez instead, he's the one who put that PR together: rust-lang/rust#52585

[killercup]

Fixed. (Sorry Guillaume you even told me about that on discord and I actually really like this despite what you might think 🙈)

Rejoice! Our rustdoc herald @QuietMisdreavus sings the cheerful lore of @GuillaumeGomez grand accomplishments:
https://twitter.com/QuietMisdreavus/status/1023416134903783429

[GuillaumeGomez]

You're all forgiven. 😛

[epage]

Got a couple ideas

• Add #[doc(inline)] in a couple places to ensure similar items are shown together rather than some being shown as re-exports
• Add a unstable_doc feature where I re-export std::process::Command and std::process::Output into a doc module. This makes it so they will show up in my docs with all extension traits visible.