code: function restoreCase (word, token) {
    // Tokens are an exact match.
    if (word === token) return token
  
    // Upper cased words. E.g. "HELLO".
    if (word === word.toUpperCase()) return token.toUpperCase()
  
    // Title cased words. E.g. "Title".
    if (word[0] === word[0].toUpperCase()) {
      return token.charAt(0).toUpperCase() + token.substr(1).toLowerCase()
    }
  
    // Lower cased words. E.g. "test".
    return token.toLowerCase()
  }
docs: Pass in a word token to produce a function that can replicate the case on
  another word.
  
  @param  {string}   word
  @param  {string}   token
  @return {Function}