Mention that VS2013 is needed
Mention that VS2013 is needed

Fixes https://github.com/rust-lang/rust/issues/29479
starsep/rust-www,azerupi/rust-www,ituxbag/rust-www,AndrewBrinker/rust-www,ituxbag/rust-www,starsep/rust-www,azerupi/rust-www,starsep/rust-www,azerupi/rust-www,ituxbag/rust-www,azerupi/rust-www,AndrewBrinker/rust-www,ituxbag/rust-www,AndrewBrinker/rust-www,starsep/rust-www,AndrewBrinker/rust-www,ituxbag/rust-www,starsep/rust-www,azerupi/rust-www,starsep/rust-www,AndrewBrinker/rust-www,AndrewBrinker/rust-www,ituxbag/rust-www