Moves to use gopkg.in/mail.v2

[paganotoni]

This is related to #795, so far it seems not to break dependencies, but we will have to test it more extensively.

[paganotoni]

Just tested this by doing the following:

• buffalo new app
• buffalo g mailer welcome
• changing properties
• calling mailers.SendWelcome() from my home handler

Do you think that is ok to say moving it to mail.v2 is ok? (this feels too easy)

[markbates]

lol, yeah, it definitely feels too easy. :)

@stanislas-m would you mind giving this a go since you found the problem originally?

[stanislas-m]

@markbates Sure, I'll test this one today. :)

[stanislas-m]

Just changed my Gopkg.toml to:

[[constraint]]
  branch = "task/moving-to-mailv2"
  name = "github.com/gobuffalo/buffalo"

Then: dep ensure

Buffalo compiles without error. 👍