added jsontags.py as a helper to serialize objects in json
converted sequential.py from yaml tags to json tags, cf https://github.com/nltk/nltk/issues/540
removed pyyaml install instructions from install.rst as it's no longer required by nltk
removed the yaml requirement from pip-req.txt as it's no longer required by nltk
added unit tests for nltk.jsontags
Merge pull request #557 from jskda/pull_request.json_tags

Pull request.json tags, cf https://github.com/nltk/nltk/issues/540
fixed stanford tagger tuple bug in python 3
allow multiple class paths for java in nltk.internals, fixed some small bugs
decode stderr in the error message for nltk.internals.java
added interface to stanford parser, c.f. https://github.com/nltk/nltk/issues/522
added batch_parse()
implementation for tagged_batch_parse()
delete file after using NamedTemporaryFile(), added comments about windows' incompatibility without using delete=False
Merge pull request #560 from jskda/pull_request.stanford_parser

Interface to stanford parser, cf https://github.com/nltk/nltk/issues/522
Merge branch 'develop' into brill

Conflicts:
	nltk/yamltags.py
updated nltk.tag.sequential tags to minimize conflict
fixed some bugs in jsontags
added json serialization implementations for the brill tagger
added backoff tagger to nltk.tag.sequential's json serialization methods so it can be serialized as well