Python 3 migration, #153 fix

Hello.

Facing with issue #153, I decided to try running hamster in python 3. After a myriad of small hacks, it works.

My current code is certainly not ready for production use - more like a proof of concept. Shall I continue working on the 2to3 migration?

waf isn't ported, so installation is partly manual:
```
./waf configure build --prefix=/usr && sudo ./waf install && sudo cp -r /usr/lib/python2.7/dist-packages/hamster/ /usr/lib/python3/dist-packages/
```