Standardize Field Names

[chewxy]

It's very obvious when you see this:

func pipeline(name string, f io.Reader) (*lingo.Dependency, error) {
	l := lexer.New(name, f)
	p := pos.New(pos.WithModel(posModel), pos.WithCluster(clusters), pos.WithStemmer(stemmer{}), pos.WithLemmatizer(fixer{}))
	d := dep.New(depModel)

	// set up pipeline
	p.Input = l.Output
	d.Input = p.Output
	go l.Run()
	go p.Run()
	go d.Run()

	select {
	case err := <-l.Errors:
	case err := <-d.Error: // should be named "Errors"
	case dep := <-d.Output:
		return dep, nil
	}
}