version increased to 0.9.7
python3.4 led into some testing-trouble, cleaned up

the shell variables and functions test did not work
with the python3.4 compatible to 2.7, as some changes
were done under the hood. Introduction of
class ConverterError led out of the trouble, compatibility
with 2.7 and 3.4 python versions reached again.
build-deps for python2,python3
rules with python2,python3 support now
changelog prepared by gbp dch, finished manually