remove mkdirp use

node 10.12 has { recursive: true }

src/backups.js

@@ -58,7 +58,6 @@ var addons = require('./addons.js'),
     fs = require('fs'),
     locker = require('./locker.js'),
     moment = require('moment'),
-    mkdirp = require('mkdirp'),
     once = require('once'),
     path = require('path'),
     paths = require('./paths.js'),
@@ -681,7 +680,7 @@ function restoreFsMetadata(dataLayout, metadataFile, callback) {
     if (metadata === null) return callback(new BoxError(BoxError.EXTERNAL_ERROR, 'Error parsing fsmetadata.json:' + safe.error.message));
 
     async.eachSeries(metadata.emptyDirs, function createPath(emptyDir, iteratorDone) {
-        mkdirp(dataLayout.toLocalPath(emptyDir), iteratorDone);
+        fs.mkdir(dataLayout.toLocalPath(emptyDir), { recursive: true }, iteratorDone);
     }, function (error) {
         if (error) return callback(new BoxError(BoxError.EXTERNAL_ERROR, `unable to create path: ${error.message}`));
 
@@ -713,7 +712,7 @@ function downloadDir(backupConfig, backupFilePath, dataLayout, progressCallback,
         }
         const destFilePath = dataLayout.toLocalPath('./' + relativePath);
 
-        mkdirp(path.dirname(destFilePath), function (error) {
+        fs.mkdir(path.dirname(destFilePath), { recursive: true }, function (error) {
             if (error) return done(new BoxError(BoxError.FS_ERROR, error.message));
 
             async.retry({ times: 5, interval: 20000 }, function (retryCallback) {