Fix the go get command.
We need to download dependencies for all packages in the repo, not just the
root (there are no packages at the root).
fixes
@@ -64,7 +64,7 @@ There is currently only one bundle of `go-libp2p`, this package. This bundle is
### Install
```bash
-> go get -d github.com/libp2p/go-libp2p
+> go get -d github.com/libp2p/go-libp2p/...
> cd $GOPATH/src/github.com/libp2p/go-libp2p
> make
> make deps
