removed doctest from compile_regexp_to_noncapturing as it doesn't work anymore
fixes unit testing bugs for https://github.com/nltk/nltk/issues/581
removed now unnecessary calls to sorted()
added back unittest & sorted, see comments: https://github.com/nltk/nltk/pull/583
added the 'flags' argument to sre_compile.compile()
Merge pull request #583 from jskda/pull_request.581

fixes unit testing bugs for https://github.com/nltk/nltk/issues/581
Merge pull request #582 from jskda/pull_request.regexp_noncapturing

Pull request.regexp noncapturing