Triggers modified event if the given filepath mod time is newer.

def trigger_modified(self, filepath):
        """Triggers modified event if the given filepath mod time is newer."""
        mod_time = self._get_modified_time(filepath)
        if mod_time > self._watched_files.get(filepath, 0):
            self._trigger('modified', filepath)
            self._watched_files[filepath] = mod_time