migrate to "export default"

also, set no-use-before-define in linter

src/storage/interface.js

@@ -11,31 +11,6 @@ import BoxError from '../boxerror.js';
 //     retry logic for upload() comes from the syncer since it is stream based
 //     for the other API calls we leave it to the backend to retry. this allows
 //     them to tune the concurrency based on failures/rate limits accordingly
-export {
-    getAvailableSize,
-    getStatus,
-
-    upload,
-
-    exists,
-
-    download,
-    copy,
-    copyDir,
-
-    listDir,
-
-    remove,
-    removeDir,
-
-    setup,
-    teardown,
-    cleanup,
-
-    verifyConfig,
-    removePrivateFields,
-    injectPrivateFields
-};
 
 function removePrivateFields(config) {
     // in-place removal of tokens and api keys
@@ -166,3 +141,29 @@ async function teardown(config) {
 
     throw new BoxError(BoxError.NOT_IMPLEMENTED, 'teardown is not implemented');
 }
+
+export default {
+    getAvailableSize,
+    getStatus,
+
+    upload,
+
+    exists,
+
+    download,
+    copy,
+    copyDir,
+
+    listDir,
+
+    remove,
+    removeDir,
+
+    setup,
+    teardown,
+    cleanup,
+
+    verifyConfig,
+    removePrivateFields,
+    injectPrivateFields
+};