More command examples
More command examples

I had trouble finding the `toolchain uninstall` command, because I didn't realize that each subcommand had their own help pages to check on. This should hopefully make it clearer for somebody in the same situation.

Closes #1362
nodakai/rustup.rs,rust-lang/rustup,rust-lang/rustup,nodakai/rustup.rs,rust-lang/rustup,inejge/rustup.rs,nodakai/rustup.rs,rust-lang/rustup,inejge/rustup.rs,inejge/rustup.rs,nodakai/rustup.rs,nodakai/rustup.rs,inejge/rustup.rs,inejge/rustup.rs,rust-lang/rustup