Remove extra dependencies

scripts/core/file.js

@@ -2,7 +2,7 @@ const { create: createPlaylist } = require('./playlist')
 const store = require('./store')
 const path = require('path')
 const glob = require('glob')
-const fs = require('mz/fs')
+const fs = require('fs-extra')
 const _ = require('lodash')
 
 const file = {}