Use gopkg.in/godo.v1 in pkg itself, godo command and generated code.

gopkg.in will only work properly if the package and command is using gopkg itself.

Imagine that at some point there's a breaking change required, either because it's needed or because it's just a new path that being taken. The `master` branch will contain these new changes and at some point be tagged `v2.0.0`. At that point people using the `v1` release with `gopkg.in/godo.v1` should still have working code, but since the pkg and cmd are now using github.com directly, they're using the `master` branch, and will probably fail to build.

I've also edited all source to use gopkg.in. Also updated the `Makefile` and `Godofile.go`.