Port the lib to Python 3

[mpiraux]

Hello,

I ported the lib to Python 3 quite easily by simply running the 2to3 tool. I also fixed a bug preventing the test suite to complete without errors.

Maybe this should not be merged directly into the master branch, but judging by the recent activity, or rather the lack thereof, I doubt that the Python2 branch will receive any future updates. Actually, moving the Python2 version in a separate branch would be the best choice in my opinion.
I intend on developing the lib further in the future. In fact I already started rewriting its internals while keeping the API untouched, but that will be the matter of another pull request.

[mpiraux]

Hello @pietercolpaert,

Any updates on this PR ? I think an up to date Python API for IRail is quite interesting, and even more since it got access to the real-time feeds :)
While the absolute gain from using this API rather than implementing it inside a Python project is quite low right now, as I said, I intend on developing it further in the future to make it more pythonic and maybe to provide more advanced functionalities.