We should probably stop trying to validate email addresses

[alaric-dotmesh]

pkg/validator/validator.go validates emails with a big long regexp; this probably does more harm than good:

• https://medium.com/hackernoon/the-100-correct-way-to-validate-email-addresses-7c4818f24643
• https://en.wikipedia.org/wiki/ReDoS

We can probably confirm the address has an @ in it and leave it at that.

[lukemarsden]

we could use https://www.mailgun.com/email-validation, at least for the SaaS