Improve / move the episode "Programming Style"

[konrad]

In our maintainer call 2019-03-20 we agreed that PEP008 and coding style should be addressed but that the current version of the episode needs be improved (but this has low priority). For the time being the episode should be kept and stay at the end of the lesson. In future the topic coding style and PEP008 could be covered earlier e.g. when explaining the different IDE for writing Python code. The current part about the assert statement should be removed as it is too advanced.