use Ewan Klein's solution to https://github.com/nltk/nltk/issues/521
some PEP-8 variable name fixes
Merge pull request #571 from jskda/pull_request.521

Pull request for  Ewan Klein's solution to https://github.com/nltk/nltk/issues/521
added an option to use regexes for find_jar()
added iterator versions of find functions in nltk.internals
use the latest model that's available instead of hard-coding the model name