Install Miniconda3-4.5.4 (Python 3.6) on Windows

[tkf]

This is a workaround for:

• https://github.com/JuliaLang/IJulia.jl/issues/739
• https://github.com/ContinuumIO/anaconda-issues/issues/10082
• https://github.com/JuliaPy/PyCall.jl/pull/556#issuecomment-421514385
• https://github.com/JuliaPy/PyCall.jl/issues/575

[tkf]

There is one failure in AppVeyor due to network problem https://ci.appveyor.com/project/StevenGJohnson/conda-jl/build/1.0.125

Except for that, it looks like it's working.

[tkf]

It works with PyCall: https://github.com/JuliaPy/PyCall.jl/pull/577

[stevengj]

Okay. We can just take out this special case when the issue is fixed upstream. (Soon, I hope?)

[tkf]

I hope so. Let's track it in #125.

[stevengj]

I forgot we did this! It's been two years, probably time to revert this patch!

In particular, it seems like Python 3.6 with breaks Tornado on Windows these days.