Clarify web2py patches

These commits clarify the exact changes made to web2py 2.8.2 and its `gluon/rewrite.py` file. That file ends up exactly the same as it was before, but storing these commits in the graph **should** record our web2py patch and how to carry it forward into newer versions of web2py.

See related discussion in https://github.com/OpenTreeOfLife/phylesystem-api/issues/121