Add test for util/ceildiv.go
Add test for util/ceildiv.go

First unit test!

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