Needs to be a way to stop the runner

We need a `#stop` method to the [AppRunner](https://github.com/polysics/matrioska/blob/develop/lib/matrioska/app_runner.rb) that:

1. Clears the `@app_map`
2. Sets a instance variable `@stopped`, that other functions check before doing anything; maybe we could use `@running` for this purpose too, but that might be confusing to read.
3. Removes the Input component created [here](https://github.com/polysics/matrioska/blob/develop/lib/matrioska/app_runner.rb#L14-L19) ?  Or some other way to clear it... preferably something that removes it so there is no hanging input watcher after the runner is shut down..