added determinism for Python 3.3

Starting from Python 3.3 onwards, dict is non-deterministic for security reasons. This [stackoverflow question](http://stackoverflow.com/questions/14956313/dictionary-ordering-non-deterministic-in-python3) goes into detail.

Some coders will need determinism (meaning, the software or simulation should produce the same output, given the same input and random seed). To make Pykov deterministic, I propose using collections.OrderedDict.