* add cache-loader to optional peer dependency ([e9d8b71](https://github.com/vuejs/vue-loader/commit/e9d8b71))
* use `require.resolve` when referencing `cache-loader` ([#1585](https://github.com/vuejs/vue-loader/issues/1585)) ([d3fa467](https://github.com/vuejs/vue-loader/commit/d3fa467))