wire: README should explain how to install Wire with modules-aware go tool

[zombiezen]

Wire's current installation documentation reads:

Install Wire by running:

go get github.com/google/go-cloud/wire/cmd/wire

and ensuring that $GOPATH/bin is added to your $PATH.

This works fine for a GOPATH-based Go tool, but in Go 1.11 with modules enabled, go get has a number of new hurdles around how to install a binary (i.e. golang/go#24250, golang/go#25922, and golang/go#27653). Once there is more consensus on those issues, we should update the Wire README with the best practices on how to make Wire available.

[zabbal]

All the abovementioned tickets are closed - perhaps it's time to removed the 'blocked' label?

[zombiezen]

Good point! go install github.com/google/wire/cmd/wire@latest is the instruction we can give reliably now.