Add/update some libraries

- Update MailHog path and description
- add envconf/gofigure/smtp/websysd/purl/go-log/goose/linkio
Sorry, I meant that since the project is documented with GoDoc, we can add the link. I originally forgot to check the project's GoDoc, and I couldn't really figure it out from its README or the project page of the original project on Google Code. But the GoDoc looks sufficient to me. If you want, feel free to revert that change or edit its link or something.