Use python3.4 instead of 2.7

This transition was done because my debian starts to link against both
installed builds of boost-python.

Signed-off-by: Jan Losinski <losinski@wh2.tu-dresden.de>
Corrent python version in README

Signed-off-by: Jan Losinski <losinski@wh2.tu-dresden.de>
Fix a copy/paste error in distance calculation

This was overseeb by some tired eyes. It caused a lot uf unneccesary
omputations because the "test only if better than best" heuristics
where disabled by it.

Signed-off-by: Jan Losinski <losinski@wh2.tu-dresden.de>