React

[petertseng]

I once wrote some potential code that could have formed the tests and example solution of the React exercise.

However, it is uncertain that I will have time to complete them sufficiently in the coming months. Thus, I'm doing a dump-and-run and closing this PR immediately after I submit it. A person seeking to port react to the track can freely choose to use any or none of this code, or any amount in between.

The tests are up to date with 2.0.0 of https://github.com/exercism/problem-specifications/blob/master/exercises/react/canonical-data.json . I did not supply a generator because I lacked the perseverance for that project. I believe a generator is technically possible, but not necessarily a prerequisite for getting this exercise on the track.

The remaining steps that would be needed before this is ready:

• Add to config.json
• README (the standard one will do)

In addition, I suggest the following:

• Consider whether an interface such as that suggested in react: Express callback expectations precisely after each set_value rust#434 would be appropriate. Specifically, that would be an interface like callback.assert_called_with 3 and callback.assert_not_called (or callback.refute_called if desired)