If you use an rss reader, the easies solution how to track a file or a folder in GitHub is by just adding .atom at the end of the url when looking at the commits.

For example: https://github.com/playframework/playframework/commits/maste... becomes https://github.com/playframework/playframework/commits/maste...

You can do that with every commit url in GitHub, be it for a folder or a file. Just add it to your rss feed reader, done.