Go Bindings Canonical Import Path

[akutz]

This patch fixes #142 and adds a Go canonical import path of "github.com/container-storage-interface/spec/lib/go/csi" to the CSI Go bindings.

@jdef @saad-ali

[akutz]

I'm closing this and we should abandon the idea of canonical imports in #142 as they are not compatible with vendored dependencies. Instead Golang dep should be used to enforce the official CSI bindings.

[cpuguy83]

There's a couple of ways we can deal with this.
If we specify go_package in the protobufs this should give us a canonical import.
Alternatively I believe we only need the canonical import path in one file in the package, in which case we can just place that in something like lib/go/csi/imports.go or something with just a package delcaration with the canonical import path.

However I would prefer if we don't modify the generated proto files after the fact.

[saad-ali]

We don't have resources to implement a redirect service at this time, and that would be required with this change. Considering 1.0 is coming up, this is not a priority.