README: do not suggest installing examples/cmd/webapp
README: do not suggest installing examples/cmd/webapp

`go get sourcegraph.com/sourcegraph/appdash/cmd/...` will install just the `appdash` command onto the path, where-as the old form `go get sourcegraph.com/sourcegraph/appdash/...` (without `cmd` suffix) would install the `examples/cmd/webapp` command as well.
bg451/appdash,joeshaw/appdash,joeshaw/appdash,bg451/appdash,bg451/appdash,joeshaw/appdash