godoc.org import paths broken

[ongardie-ebay]

Beam requires a GOPATH set to the root of the repo, but godoc.org doesn't seem to get that.

• We have to use https://godoc.org/github.com/eBay/beam/src/github.com/ebay/beam to get to the docs, rather than https://godoc.org/github.com/eBay/beam.
• facts, msg, tools, and util are directories that don't contain any go files, and godoc.org doesn't appear to discover them on its own. We might be able to work around this by adding doc.go files to those directories.
• Our import paths on godoc.org are all broken, so links between package types don't work. I don't know what we can do about that without moving away from GOPATH.

[superfell]

Moving to go modules would help on this, but then dealing with the .proto's is problematic. The modules directory tree has version numbers in the directory names, and so that breaks proto import paths, and the module version of vendor only vendors .go files. You'd need the makefile to carefully construct a new directory tree for the .proto files, or at least for the dependencies (primarily the google types & goto photo)