Auto merge of #8262 - alexcrichton:unstable-docs, r=ehuss
Auto merge of #8262 - alexcrichton:unstable-docs, r=ehuss

Document unstable `strip` profile feature

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