Compiling the whole tui stack, just to debug the lua command line seems
counterproductive to me. This allows to just compile the needed parts
for a basic lua repl.
As of yet the repl is just a mock-up, as the event handling can, as of
right now, not easily be separated from the tui.
To activate specific features add specify the on the cargo command line
like this:
```
cargo run --features "cli tui"
```
or add them to the `default` feature set in the `Cargo.toml`.