function ownKeys(object, enumerableOnly) {
    var keys = Object.keys(object);

    if (Object.getOwnPropertySymbols) {
      var symbols = Object.getOwnPropertySymbols(object);
      enumerableOnly && (symbols = symbols.filter(function (sym) {
        return Object.getOwnPropertyDescriptor(object, sym).enumerable;
      })), keys.push.apply(keys, symbols);
    }

    return keys;
  }
Font Awesome 4 used the prefix of `fa` for all icons. With the introduction
of new styles we needed to differentiate between them. Prefix `fa` is now an alias
for `fas` so we'll ease the upgrade process for our users by automatically defining
this as well.