[web] Update packages, use TS 2.4

web/web.py

 #!/usr/bin/env python
 # Copyright 2016 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
 """Manages web/ resource checkout and building.
 
 This script can be run in one of three modes:
   - As "initialize.py", it will perform resource dependency checkout for
     "luci_deploy" and quit.
@@ skipping 43 matching lines @@
   system. Please install Node.js and NPM. Installation instructions can be found
   at:
       https://docs.npmjs.com/getting-started/installing-node
   """
       raise Exception('Unable to locate Node.js installation.')
     tc = cls(web_dir, *node_js)
 
     # Install NPM deps from "package.json".
     def install_npm_deps():
       tc.npm('install', cwd=web_dir)
+      tc.npm('prune', cwd=web_dir)
     cls._call_if_outdated(
         install_npm_deps,
         os.path.join(web_dir, '.npm.installed'),
         os.path.join(web_dir, 'package.json'),
         [os.path.join(web_dir, 'node_modules')],
         force)
 
     # Install Bower deps from "bower.json".
     def install_bower_deps():
       tc.bower('install', cwd=web_dir)
@@ skipping 214 matching lines @@
     return _main_initialize(args)
   elif script_name == 'build.py':
     return _main_deploy(args)
   else:
     return _main(args)
 
 
 if __name__ == '__main__':
   logging.basicConfig(level=logging.INFO)
   sys.exit(main(sys.argv))