Fix Docker instructions in README
Need to set NATS_URL=localhost so that the nats-* commands can find the
NATS server running locally
@@ -168,7 +168,7 @@ $ docker run -ti --rm --entrypoint /nats-server --name js synadia/jsm:latest -js
And in another log into the utilities:
```
-$ docker exec -ti js sh -l
+$ docker exec -ti -e NATS_URL=localhost js sh -l
```
This shell has the `jsm` utility and all other NATS cli tools used in the rest of this guide.
