WIP: fixing pyflakes / pep8, trying to improve readability

This addresses #645 
@josef-pkt I keept the power operator the way you use to write it.

Besides adding white spaces around operators / removing them for kwargs, deleting duplicate imports, enforcing line breaks where needed (> 80 characters)
I also applied the following measures to improve readability:
- multi line strings instead of adding to string
- intermediate results instead of long functions calls
- implicit tuple construction

Tell me what you think about it.

I thinks I found / fixed the most 'disturbing' issues.
Still I'm wondering about the many comments not related to the examples e.g., todo, etc.