Prepare for Python 3.x support
- Use print function
- Use compability methods from six

- If database lag exceeds max lag, the API will still send 200, not 503.
  This was only added to documentation after bugzilla:31156.
  Ref. <https://www.mediawiki.org/wiki/Manual:Maxlag_parameter>
- In addition, Requests doesn't raise an exception when status code != 200
  unless raise_for_status() is called, so we should call that to catch
  any other 5xx errors such as Squid errors.
- Replace print statements with logging

Note that responses>=0.3.0 is needed to run the test suite now

As suggested in #52
Original auth mechanism introduced in #27
This change should retain backwards compability

Use new token handling system described on
https://www.mediawiki.org/wiki/API:Meta#tokens for MediaWiki >= 1.24

Work in progress, looks a bit dirty right now

Since we now require MediaWiki 1.16, these are no longer needed. It
might be necessary to add new compability methods in the future, but the
API is generally stable now.

- Require 'ordereddict' only on Python < 2.7
- Don't require 'simplejson'

- For some reason, 'pytest-cache' isn't found by setup.py if not
  specified explicitly in 'tests_require'
- Add tox.ini so tests can be run using tox if desired
- Update test to not be dependent on serialization

- A single command `python setup.py test` will now install test
  dependencies, make an in-place build and run the tests.
- The setup script now requires Setuptools. A message will be printed
  if it is not found.

- Note the following exception replacements:
  mwclient.errors.HTTPError -> requests.exceptions.ConnectionError
  mwclient.errors.HTTPStatusError -> requests.exceptions.HTTPError
  mwclient.errors.HTTPRedirectError -> requests.exceptions.TooManyRedirects

- Removed the `compability.old_upload` method, which was used for
  MediaWiki < 1.16.

- Requests automatically decompresses gzip-encoded responses, and
  does its best to decode response content to unicode when possible.

- [#53] Using the Responses library to mock http requests in tests

- Keep automated tests to be run with py.test in './tests/'
  and examples in './examples/'
- Rename test to adhere to 'Conventions for Python test discovery'
  (http://pytest.org/latest/goodpractises.html#test-discovery)