Language runner should list available languages if given doesn't match

[ctsstc]

Currently if you try a language that it does not know it just says:

Unknown language: someLanguage

It would be nice if it listed the available languages like:

Unknown language: someLanguage
Try one of these: nim, rust

[ctsstc]

Start with branch: 141-language-runner-list-available-languages-on-no-match as your base which includes a failing test that you can get passing.