Fix IP.__cmp__ if argument is not an IP

IP.__cmp__(other) doesn't raise an exception anymore if other is not an IP object
Add IP.get_mac() method: get the 802.3 MAC address from IPv6 RFC 2464 address
only __eq__ accepts non-IP objects, not __lt__
Add IP.__ne__(other) method
Fix ipversion in IP.__getitem__()

Issue #12: Fix IP('::/0')[0]: return an IPv6 instead of an IPv4 address
prepare version 0.76
Python 3 does not need 2to3 conversion anymore

+* Drop support of Python older than 2.4
Merge various cleanups from https://github.com/toofishes/python-ipy

Conflicts:
	IPy.py
Fix several issues with adding IP ranges

* Prevents non-adjacent ranges from being added
* Prevents creating invalid subnets
* Fixes a bug where the integer value of an IPv6 address that is less than
  32 bits would be treated as an IPv4 address during addition.
add IPSet; add IPint().__sub__, move IP.__add__ to IPint().__add__
Cleanup ChangeLog format; add missing notes
Prevent IPv4 and IPv6 addresses from reporting that they can contain each other.
Optimized IPSet.__contains__, added tests. Stopped copying for IPSet.__iter__.
Fix regression with long() creeping in from 07ff989747b7a41c1ad1839732595a658e1cb493
Accept instances of IP in overlaps()
Add conversion between mapped v4 addresses
v46map(): add method documentation, ChangeLog entry
Update AUTHORS
Update changelog, test for sort order
Release 0.80