Changing "$target" to "ci" in the readme
Per issue:
@@ -71,7 +71,7 @@ as `booklit.yml`, [target your Concourse
instance](https://concourse-ci.org/fly.html#fly-login), and then run:
```sh
-fly -t $target set-pipeline -p booklit -c booklit.yml
+fly -t ci set-pipeline -p booklit -c booklit.yml
```
These pipeline files are self-contained, maximizing portability from one
