Here is the direction I am wanting to take this:

descriptor.blob is regenerated if data.proto is newer.

data.pb.go is regenerated if data.proto is newer.

Letting Make's newness handler deal with this seems relatively idiomatic to me.  The idea should be that in the build process nobody should need ``protoc`` installed unless he or she is updating the .proto IDL.  This starts moving us closer to a pure ``go get`` installation process.