Also replace already hashed filenames

In my project I needed to overwrite the asset references without exporting it to a build folder. The grunt task ended up prepending the hash to these filenames causing this effect: ```'/css/79bc7f6e.79bc7f6e.79bc7f6e.theme.css'```

I've updated the regexp in the task to also find prepended hashes to replace, so any existing hashed filename will be updated to the new version when saving.