Added KGMLCanvas import map test (and minor changes elsewhere)

This PR adds a test for use of `KGMLCanvas(pathway, import_imagemap=True)`, which should cover for the typo bug in `KGML_vis.py` discovered in 1.65.

There are also minor additions to comments, and changes for pep8 compliance, in `KGML_pathway.py`.
Stray leading space on docstring. Also when just one line can put the closing triple quote on the same line as in example in PEP 257 https://www.python.org/dev/peps/pep-0257/