Allow setting a flat array as options

[ericdfields]

e.g. ['Dog', 'Cat', 'Mouse', 'Squirrel']

Option list would look like

<option>Dog</option>
<option>Cat</option>
<option>Mouse</option>
<option>Squirrel</option>

Native browser behavior is to use the "label" value if there isn't a set value.

I have a couple flat lists in my app like this. Right now I have to add little methods like this to get around it:

    const optionsToHash = options.map((opt) => {
      return { value: opt, label: opt }
    })

NBD, but most select widgets do this.

I'll also try to put in a PR for this, as the library otherwise suits my needs swimmingly.