Consider `rib` support for `console` command

[`rib`](https://github.com/godfat/rib) is a new light-weight and pluggable REPL alternative that could easily be considered in the [`console` commands startup script](https://github.com/technekes/nib/blob/master/lib/nib/console.rb#L5-L28) (which could use some refactoring :heart:).