Merge pull request #3 from nltk/master

Merge updates from NLTK master
SemcorCorpusReader was returning incomplete sense information

semcor.py was creating lemma sense tags as strings of the form `<lemma>.<sensenum>`, which is incorrect: the sense number is actually POS-specific. With this fix, SemcorCorpusReader tries to retrieve the Lemma object directly from WordNet (using the sense key). If that fails, a string of the form `<lemma>.<pos>.<sensenum>` is given.
pass wordnet corpus reader to semcor corpus reader
Merge pull request #1 from nschneid/patch-11

pass wordnet corpus reader to semcor corpus reader
corpus.doctest: update for semcor
Merge pull request #2 from nschneid/patch-11

corpus.doctest: update for semcor
except Exception
changed tree node property to a method, and added a set_node method (following the model of prob/set_prob etc in probability.py)
fix the node setter in ImmutableTree
Merge branch 'master' of https://github.com/stevenbird/nltk
Merge branch 'master' of https://github.com/nltk/nltk
Tree.node() and Tree.set_node() changed to Tree.label() and Tree.set_label(); Tree.node() raises notImplementedError
removed emacs files inadvertently included with commit
use label() method in place of node attribute
Merge pull request #502 from stevenbird/master

change tree node property to a method
Fixed bug in code to find right peak; resolves https://github.com/nltk/nltk/issues/408
Removed warning that is generated when scikitlearn is not installed; resolves https://github.com/nltk/nltk/issues/498
changed Synset and Lemma properties to methods, cf https://github.com/nltk/nltk/issues/475
Fixed minor inconsistency in A expansion rule.
changed chunkparser api to use root_label and chunk_label instead of top_node and chunk_node