stem_word and lower case stem output in v3.2.2

Hi,

Just wanted to confirm the following things affected by the recent upgrade to v3.2.2:

• There is no stem_word function in PorterStemmer(). I had to replace it with stem()
• Unlike before, stem returns lower case of a word e.g. stem for Stemming (http://text-processing.com/demo/stem/ is the same as before).

Cheers, Ehsan

[alvations]

Closing issue, https://github.com/nltk/nltk_book/pull/216 is merged =)

Thanks @iranianpep @jayvdb @RodgerKibble for raising the issue! Thanks @ExplodingCabbage for verifying the changes!

[alvations]

Validating the outputs from Chapter 3.6 of the book.

>>> from nltk import word_tokenize
>>> from nltk.stem import PorterStemmer
>>> porter = PorterStemmer()

>>> raw = """DENNIS: Listen, strange women lying in ponds distributing swords
... is no basis for a system of government.  Supreme executive power derives from
... a mandate from the masses, not from some farcical aquatic ceremony."""

>>> tokens = word_tokenize(raw)

>>> [porter.stem(t) for t in tokens]
['denni', ':', 'listen', ',', 'strang', 'women', 'lie', 'in', 'pond', 'distribut', 'sword', 'is', 'no', 'basi', 'for', 'a', 'system', 'of', 'govern', '.', 'suprem', 'execut', 'power', 'deriv', 'from', 'a', 'mandat', 'from', 'the', 'mass', ',', 'not', 'from', 'some', 'farcic', 'aquat', 'ceremoni', '.']

The other example using IndexedText doesn’t change since it’s not printing the direct output of the porter.stem().

Changes suggested on https://github.com/nltk/nltk_book/pull/216