README.md: Move Building section forward, require Go >= 1.2
README.md: Move Building section forward, require Go >= 1.2

CodyGuo/elvish,CodyGuo/elvish,elves/elvish,ke7ofi/elvish,beni55/elvish,elves/elvish,ke7ofi/elvish,elves/elvish,beni55/elvish,elves/elvish,elves/elvish