Sync mtime with updated time

For issue #311 
storage.key.get_contents_to_filename will sync file's mtime and metadata's updated time 
This is our least favorite feature of `pylint` (complaining about indents like this). Please change to
```python
        mtime = time.mktime(
            datetime.datetime.strptime(
            self.properties['updated'],
            '%Y-%m-%dT%H:%M:%S.%fz').timetuple()
        )
```