No invalid email

Addresses issue #[635](http://daringfireball.net/projects/markdown/syntax#link) 
It is OK, just description is not OK. Start with a capital letter. Capitalize `displayName` correctly. And there is no need to add to the name that it is for `User` document. Because migration is added onto a document, but is independent. So you could reuse same migration for multiple documents. And when a migration is stored in the log, it is stored for each document separately, so it is clear that it is for `User` document.