replace underscore with our own

we only need like 5 simple functions

src/users.js

@@ -103,7 +103,7 @@ const appPasswords = require('./apppasswords.js'),
     superagent = require('superagent'),
     util = require('util'),
     validator = require('validator'),
-    _ = require('underscore');
+    _ = require('./underscore.js');
 
 const CRYPTO_SALT_SIZE = 64; // 512-bit salt
 const CRYPTO_ITERATIONS = 10000; // iterations
@@ -191,7 +191,9 @@ function validatePassword(password) {
 
 // remove all fields that should never be sent out via REST API
 function removePrivateFields(user) {
-    const result = _.pick(user, 'id', 'username', 'email', 'fallbackEmail', 'displayName', 'groupIds', 'active', 'source', 'role', 'createdAt', 'twoFactorAuthenticationEnabled', 'notificationConfig');
+    const result = _.pick(user, [
+        'id', 'username', 'email', 'fallbackEmail', 'displayName', 'groupIds', 'active', 'source', 'role', 'createdAt',
+        'twoFactorAuthenticationEnabled', 'notificationConfig']);
 
     // invite status indicator
     result.inviteAccepted = !user.inviteToken;
@@ -596,8 +598,6 @@ async function update(user, data, auditSource) {
 
     if (constants.DEMO && user.username === constants.DEMO_USERNAME) throw new BoxError(BoxError.BAD_STATE, 'Not allowed in demo mode');
 
-    if (_.isEmpty(data)) return;
-
     if (data.username) {
         // regardless of "account setup", username cannot be changed because admin could have logged in with temp password and apps
         // already know about it