I don't have the Steam version but what I do is use grunt to upload my scripts whenever I save in my IDE. To keep things versioned and available to those seeking inspiration I also push to github. If you want to have Screeps pull code from GitHub you could have your working directory somewhere else than your screeps directory.

Screeps won't pull any code before you link your repo. 

I wrote a small program to download all scripts from a branch in one click.

https://github.com/Frederikam/Screeps-Script-Downloader

I agree. Same should apply to spawners