[dev] [DISCUSS] Python 3.6 support

[anthony shaw]

I just merged a PR to add Python 3.6.0 to the build, now that it's released. 
The build failed the first time, the function spec of showwarning in the 
warnings.py changed, but we only used it within a test module so I would say it 
works fine in 1.5.0 release bits
We can say that 3.6 is experimental in 1.5 and then have it as supported in 
1.6? What do people think?
Also, a few of us need to use 3.6 in anger and check for any issues. 
Regards
Anthony Shaw