Ignore .venv
Change __repr__ to comply with standards.

@exhuma requested that the __repr__ output for IpRange be changed to match the
conventions documented at
http://docs.python.org/2/reference/datamodel.html#object.__repr__
Exit with non-zero status when tests fail.

Apparently unittest.TextTestRunner() doesn't exit with a non-zero status when
there are failing tests by default. Sad panda. My all tests are always green
status was a sham.
Replacement for bin() in python <2.6.

The bin() function was introduced in Python 2.6. Added an existence check for
this built-in and a substitute implementation from
http://code.activestate.com/recipes/219300/#c7.
Test changes for better version compatibility.

- Removed unicode literal tests for Python >3 && <3.3.
- Removed buffer test for Python >3.
- Added +IGNORE_EXCEPTION_DETAIL for PyPy None type tests.
Add Python 3.3 as a TravisCI test target.
Merge pull request #4 from bd808/features/repr-format

Landing repr format change feature branch.