added test case; removed non-ascii chars; did some documentation

Hi Roland,
I had rebased my local fork and redone the "removed non-ascii char \xfe" commit. This is now included twice, and I do ot know how to remove it from github. Please ignore one of the two.

Friday, 11 July: I added a new test case with a new class and a few changes in base.py that have an impact on code exeution. To help my understanding of the code, I did a bit of refactoring - I hope that this was not too intrusive.