Update INSTALL file to include py3.6 #7697
Description
The line
:term:`python` 2.7, 3.4, or 3.5
can trivially be updated but someone needs to check what compiler to add in the paragraph that says
The Python shipped from http://www.python.org is compiled with Visual Studio
2008 for versions before 3.3, Visual Studio 2010 for 3.3 and 3.4, and
Visual Studio 2015 for 3.5. Python extensions are recommended to be compiled
with the same compiler.