Option parsing is too eager

Test case: Run `rspec` with this `.rspec` file:

```
--format d --order random -I ./app/models -I ./app/services -I ./app/contexts --I ./app/repositories
```

When you do, rspec will repeatedly try to run as if you'd specified "rspec --init". That's because the last option in the `.rspec` file is typoed; it should be `-I` instead of `--I`.

As a result, the option is parsed as if you'd typed `--init`, but you meant `-I`.

Suggestion: rspec should only parse options exactly as written, with no coercion. It should be an error to specify an option that is not recognized exactly.