Deprecated nodemailer version

Hi,

The package.json requires nodemailer@2.7.2. When running npm, it states that all versions below 4.1.0 are deprecated and links back to https://nodemailer.com/status/ (which says that nodemailer is no longer maintained).

I did a quick search for API changes between nodemailer versions but could not find anything tangible. I'll try to update and see if everything still works.

There is also a warning about node-uuid which is deprecated in favor of uuid, but this is coming from a NPM package and not Kresus itself.