minimum Python version changing to from 2.3.x to 2.4.x

[David Moss]

I've had a deeper look into bug ticket 30 - http://code.google.com/p/netaddr/issues/detail?id=30.

The use of the set class is not the only problem with netaddr running
on Python 2.3.x. A lot of unit tests are also failing and a number of
the following warnings are also being generated :-

FutureWarning: x<<y losing bits or changing sign will return a long in
Python 2.4 and up
FutureWarning: hex()/oct() of negative int will return a signed string
in Python 2.4 and up

These issues appear to centre around the use of hexadecimal literals
greater than sys.maxint. It looks like this behaviour changed
significantly in Python 2.4.

In light of this, I propose bumping the minimum Python version for
netaddr to 2.4.x going forward. As Python 2.6 is now out it's probably
reasonable to drop support for 2.3.x without causing problems for too
many users.

Please shout if this is going to cause issues for anyone and we can
review this decision if required.

Dave M.