Working with Code 2015 using Sharepoint 365

This (please refer to the steps below) will work only if you use IE as your internet browser. 

1. Open your Sharepoint site (Site Collection).
2. Click on Documents in the left pane menu.
3. Click Library on the tab above.
4. In the Ribbon menu, locate "Open with Explorer" and click it.
5. Once the Windows Explorer opens, copy the url
6. Click Map Network Drive from Windows Explorer's left pane and paste this URL.
[7. Check if Keep me signed in option had been checked when you logged into your Sharepoint site otherwise, an error may occur. If it still does not work, check if your Sharepoint site is added to your browser's Trusted sites].
8. Open Visual Studio Code or copy/paste your existing VS Project to this location.
9. Microsoft's OneDrive will take care of syncing the files/folder with your Sharepoint Document Library.

So, beyond Napa 365 and Visual Studio 2012 Ultimate, you can now also use the lightweight super IDE - Code!

Happy Code-ing !