Migrate from gb to go modules

[johanhugg]

Hello,

It doesn't seem like gb is being actively worked on, would it be interesting to move away from gb to a traditional go build?

I've created a fork that uses dep for dependencies and I also fixed some issues with "multiple" imports (go build didn't like the existence of both github.com/Sirupsen/logrus and github.com/sirupsen/logrus)

https://github.com/johanhugg/go-neb