wip: python3 support

[dtkav]

Hi friends. I've been enjoying using cosmolog in python 3.

Here are some changes I needed in order to support python 3.
I've been testing them in a cosmolog-dtkav package.

This might work nicely with #2 (adds tox support).

Regarding the changes:

• exception.message was deprecated in python 2.6 (args[0] uses the first argument to the exception, usually the 'message')
• python3 doesn't have long, so six.integer_types is (int,) in python3 and (int, long) in python2
• basestring is replaced by six.string_types
• six.iteritems(...) replaces iteritems()

[dtkav]

@isilien @bcavagnolo if you have some time to take a look, I'd really appreciate it!

[bcavagnolo]

LGTM @dtkav. Let me try to merge #2 first....

[bcavagnolo]

@dtkav can you rebase to master and add the python3 env you're testing with?