direct mode

```
$ cinaps -i src/nodes.cxx
File "src/nodes.cxx", line 1, character 0:
Error: the direct mode of cinaps is no longer supported. Please use the "cinaps" stanza in your dune file instead.
```

I hoped to be able to use it in a c++ project but apparently it is now limited to dune only? If this decision is irreversible then treat this as a feature request to update README :]