Pos tagger

I noticed that your code failed for Python 3 on this line. In case you were wondering, you could use the [`six`](https://pythonhosted.org/six/) module to do [`from six import StringIO`](https://pythonhosted.org/six/#six.StringIO) which will mask this compatibility issue for you. That may mean there are still other compatibility issues you would need to tackle, but I wanted to point out that you do have options.