Scrapinghub

------------------

- fix `iter` logic when applying single `count` param

------------------

- add support for TZ-aware datetime objects
- better tests

------------------

- add a client parameter to disable msgpack use
- add VCR.py json-serialized tests
- make `parent` param optional for requests.add
- improve documentation

------------------

- `python-hubstorage`_ merged into python-scrapinghub
- all tests are improved and rewritten with py.test
- hubstorage tests use vcrpy cassettes, work faster and don't require any external services to run

`python-hubstorage`_ is going to be considered deprecated,
its next version will contain a deprecation warning and a proposal
to use python-scrapinghub >=1.9.0 instead.

------------------

- python 3 support & unittests
- add retries on httplib.HTTPException
- update scrapinghub api endpoint