Removing TAG as a part of speech tag.

Both metanl.english and ProcessWrapper in metanl.extprocess, instead of
treating "#word" and "@word" as special unstemmed tokens with the part of
speech "TAG", will now give them the stems and parts of speech they would have
had without the leading # or @.

Also removing some unused imports from metanl.english, while I was in there.
Treat @-mentions like #-tags in metanl.english
Merge branch 'taglessness' into Py3

Conflicts:
	metanl/nltk_morphy.py
Merge branch 'Py3' of github.com:commonsense/metanl into Py3
Simplification of nltk_morphy tag_and_stem
Copy docstring tests into test files