Incomplete package conversion to github.com/containerd/typeurl

[nim-nim]

+ go test -buildmode pie -compiler gc -ldflags ' -X github.com/containerd/typeurl/version.commit=f6943554a7e7e88b3c14aad190bf05932da84788 -X github.com/containerd/typeurl/version=0 -extldflags '\''-Wl,-z,relro  '\'''
# github.com/containerd/typeurl
marshal_test.go:9:2: cannot find package "github.com/containerd/containerd/typeurl" in any of:
        /usr/lib/golang/src/github.com/containerd/containerd/typeurl (from $GOROOT)
        /builddir/build/BUILD/typeurl-f6943554a7e7e88b3c14aad190bf05932da84788/_build/src/github.com/containerd/containerd/typeurl (from $GOPATH)
        /usr/share/gocode/src/github.com/containerd/containerd/typeurl
FAIL    github.com/containerd/typeurl [setup failed]

[elboulangero]

Related to #2 it seems

[kzys]

This should be resolved by #9.