Proposed resolution for issue 395

See [Issue 395](https://github.com/nltk/nltk/issues/395)

Currently lowest common hypernyms do not return a result based on the
hypernym paths of the 2 synsets. So there may be a "better" result when
taking into account the hypernym paths.

    >>> from nltk.corpus import wordnet as wn
    >>> wn.synset('policeman.n.01').relative_lowest_common_hypernyms(wn.synset('chef.n.01'))
    [Synset('person.n.01')]
    >>> wn.synset('policeman.n.01').lowest_common_hypernyms(wn.synset('chef.n.01'))
    [Synset('organism.n.01')]

I'm not sure if this will be considered useful or not, but I thought this approach might make sense. Of course, I'm open to changes and suggestions.