Truncate does not work for blocks of text

[erikgeiser]

All the functions referenced in the README.md are advertised to work on blocks of text, but truncate does not:

package main

import (
	"fmt"

	"github.com/muesli/reflow/truncate"
)

func main() {
	test := "123456789\nhidden"
	fmt.Println(truncate.String(test, 5)) // output: 12345
}