Changed test_wordnet.py to wordnet_lch.doctest

Possible resolution to [issue 445](https://github.com/nltk/nltk/issues/445)

I tested this on OS X with Python 2.7, and with Python 3.3. In Python 3.3 the test fails with this error:

    ... line 45, in wordnet_lch.doctest
    Failed example:
        wn.synset('woman.n.01').lowest_common_hypernyms(wn.synset('girlfriend.n.02'), use_min_depth=True)
    Expected:
        [Synset('woman.n.01'), Synset('organism.n.01')]
    Got:
        [Synset('organism.n.01'), Synset('woman.n.01')]

What is the best way to resolve this problem? I don't know why the list is coming back in a different order in Python 3, but should I just change it to something like this which should work for both?

    set(wn.synset('woman.n.01').lowest_common_hypernyms(wn.synset('girlfriend.n.02'), use_min_depth=True))

Personally, I'd rather if it "just worked". Thank you for your advice. Also, I'm not sure that the version numbers I mentio are correct.