Fund PyInstaller development

GRR uses PyInstaller for distributing installable packages.

PyInstaller is in urgent need of funding:

**If reasonable funding is not achieved for PyInstaller until end of January 2020, @htgoebel will retire as an maintainer.** This basically means: Unless somebody else steps in, there will be nobody reviewing any pull-request, there will be not improvement and sooner or later you will not be able to use PyInstaller any more.

For details see https://github.com/pyinstaller/pyinstaller/issues/4404.