Sometimes, other importers don't add dates to converted files. A small fix.

I used WP -> Octopress before, and it didn't import all dates. This led to the JSON having no 'created by' which is _required_ by Ghost to import posts.

I wrote a small fix here:

``` python
...
post_tag_id = post_tag_id + 1
else:
pass
else:
raise Exception('Unexpected exception!')

// Get times if none found
createdAt = post.get('created_at', int(time.mktime(datetime.datetime.strptime(markdown_file[7:17] + ' 00:00', "%Y-%m-%d %H:%M").timetuple()) * 1e3))

post["created_at"] = createdAt
post["updated_at"] = createdAt
post["published_at"] = createdAt
```

This works due to the fact that filenames themselves have some part of the date - It parses them and assigns the time at 12 o' clock of that day.

It's an ugly solution since I'm pathetic at python, but should work.