readme: switch example tag use to 'nautilus'
Switch the example of how to compile go-ceph with tags to refer to
nautilus in light of luminous and mimic being deprecated.
Small wording/grammar changes to try and make the sentence clearer.
@@ -23,13 +23,14 @@ only be available in recent versions, and others may be deprecated. In order to
work with non-current versions of Ceph, it is required to pass build-tags to
the `go` commandline. A tag with the named Ceph release will enable/disable
certain features of the go-ceph packages, and prevent warnings or compile
-problems. E.g. build against libcephfs/librados/librbd from Mimic, or run `go
-test` against Limunous, use:
+problems. For example, to ensure you select the library features that match
+the "nautilus" release, use:
```sh
-go build -tags mimic ....
-go test -tags luminous ....
+go build -tags nautilus ....
+go test -tags nautilus ....
```
+
## Documentation
Detailed documentation is available at
