code: function getText(fieldBoost, doc) {
    var text;
    if (!fieldBoost.deepField) {
      text = doc[fieldBoost.field];
    } else { // "Enhance."
      text = doc;
      for (var i = 0, len = fieldBoost.deepField.length; i < len; i++) {
        if (Array.isArray(text)) {
          text = text.map(handleNestedObjectArrayItem(fieldBoost, fieldBoost.deepField.slice(i)));
        } else {
          text = text && text[fieldBoost.deepField[i]];
        }
      }
    }
    if (text) {
      if (Array.isArray(text)) {
        text = text.join(' ');
      } else if (typeof text !== 'string') {
        text = text.toString();
      }
    }
    return text;
  }
docs: given an object containing the field name and/or a deepField definition plus the doc, return the text for indexing