How to build app for web without debug info?


I just started a sample app from tabs template and www directory is ~5.5MB. It takes almost a minute to load on regular 3G connection, while user is staring at a blank screen. main.js and main.css takes longest time to load.
Is there any way to build project for deployment and to minimize app footprint? Is it possible to split css by platform and load only appropriate css when needed (iOS user doesn’t need Android and Windows themes). What about unused javascript?
Forgot to mention that I’m building a progressive web app, that’s why small size and fast download is a must.