declare module "slugify" {
  declare type SlugifyOptions = {
    replacement?: string,
    remove?: ?RegExp,
    lower?: boolean,
    ...
  };
  declare module.exports: {
    (input: string, optionOrReplacement?: string | SlugifyOptions): string,
    extend({ [key: string]: string, ... }): void,
    ...
  };
}
