Check spelling of `word`.
function spell(word) {
  var self = this
  var dict = self.data
  var flags = self.flags
  var value = form(self, word, true)

  // Hunspell also provides `root` (root word of the input word), and `compound`
  // (whether `word` was compound).
  return {
    correct: self.correct(word),
    forbidden: Boolean(value && flag(flags, 'FORBIDDENWORD', dict[value])),
    warn: Boolean(value && flag(flags, 'WARN', dict[value]))
  }
}