Adding pageid, contentmodel, pagelanguage, restrictiontypes as attributes of Page

Thoses attributes were only accessible through private _info dict.

pageid was only accessible through the 'private' _info dict.

Add support for querying the CheckUser log

Handling requests exceptions is the responsibility of `Site.raw_call()`,
not `Site.upload()`

Add a null handler to prevent 'No handlers could be found for logger
"mwclient.*"' warnings. This seems to be good practice for libraries.

When rctoponly is set only changes which are the latest revision are listed.

fix PageList API arg passing to GeneratorList

PageList wasn't adding the 'g' prefix to API arguments it
passes to GeneratorList, and GeneratorList doesn't do that
itself. This fixes it.

Adds six as requirement. It solves "ImportError: No module named six"

Conflicts:
	mwclient/listing.py

Quite silly, but until the problem is fixed on the server side,
it seems like this workaround is the best solution there is.

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

Back-ported to Python 2.6 and 2.7

Conflicts:
	RELEASE-NOTES.md