Force generateCache to run on every request

[cdeutsch]

Every time I change a javascript file or CSS file it takes two refreshes for it to appear in the browser. It looks like fs.watchFile picks up the change (running OSX) but generateCache is being called after the old content is already served.

[dawnerd]

I had a pull request that changed fs.watchFile to use the new fs.watch api. Does it still happen with this?