update dependencies and make Store implementation compatible with rdflib 4.0
drop python 2.4 and 2.5 support
add python 3 support
quick note about upgrading
increase major version to highlight backwards incompatibility
update toxin
Merge commit '89f9360afc2d0e0f91d45e586d404146b35e3d05'

Conflicts:
	README.md
	rdflib_zodb/ZODB.py
	setup.py
	tox.ini
use nose  to run py3 tests
add pypy to fox
don't install ZODB for python3 as ZODB < 4.0 does not support it.
add py 3.2 ands 3.3 to travis
Merge pull request #1 from gweis/master

update rdflib-zodb to rdflib4