Auto merge of #7407 - ehuss:update-unstable, r=alexcrichton
Auto merge of #7407 - ehuss:update-unstable, r=alexcrichton

Update some unstable docs

Some minor updates.

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