Digitally sign executable with Windows signtool.exe

[Scott Werner]

References:

• https://msdn.microsoft.com/en-us/library/windows/desktop/jj835835(v=vs.85).aspx
• https://github.com/pyinstaller/pyinstaller/wiki/Recipe-Win-Code-Signing

[Scott Werner]

Code signing done by signtool.exe and instructions for it found on README.