Added codning: utf-8 tag to setup.py

This is needed to build PyMC against Python 3.
Fixed implicit integer devision

This fixes some cases where the new devision in Python 3 returns
floats instead of integers.

I replaced each of the cases that I found with an `//` to ensure that
an integer is returned.
Wrapped dict.(values|list|keys)() in list()

This is nessecary in some cases, because in Python3 these methods
do not return lists.
Wrapped range() in hpd in list()

This is necessary, because Python3 returns an iterator from range
rather than a list.
Reactivated Python 3.3 on travis
Merge pull request #495 from tobeplugged/py3k

Making PyMC 2.3 run on Python 3.3