Ease subclassing : PostqueueStore.MailClass attr.

Currently, if I want to subclass `store.PostqueueStore` and `store.Mail`, I have to rewrite entire methods just to change the `store.Mail` className. That's bad for maintenance.

That proposal is to make it a class attribute, easing the subclassing.
Merge pull request #2 from JocelynDelalande/patch-1

Ease subclassing : PostqueueStore.MailClass attr.
Merging Jocelyn Delalande's pull request to v0.5.2 dev
SphinxDoc configuration is now Python3 compliant
setup.py is now Python3 compliant
Bump to version 0.5.2 with uptodate documentation
Merge branch 'dev_v0.5.2'
added postsuper commands to pqshell
bugfix: the postsuper operations lacked a separator between qids
Merge pull request #6 from oasiswork/postsuper-ops-in-pqshell

added postsuper commands to pqshell
2to3 raw output

Conflicts:
	bin/pqshell
	pyqueue/__init__.py
	pyqueue/control.py
	pyqueue/shell.py
removed unneeded list conversions and shortened dict keys lookups to be python-3 style
file() do no longer exists in python3

Conflicts:
	setup.py
fixed issues with encoding of std* communications in python3

Conflicts:
	pyqueue/control.py
	pyqueue/store.py
drop the use of deprecated Exception.message, no longer working with python3