Improve setup experience on windows

[idan]

See heroku/herokudata#409 for some context

[msakrejda]

Philipe Navarro who is contracting with the CLI team got this working on windows "but it was a mess":

steps:
- Install python2.7
- PATH and PYTHONPATH python2.7
- Install node/npm 6.X (will path for you)
- Open cmd as administrator, `npm install —global windows-build-tools`
- Install .NET Framework 4.5.1 (on windows 7)
- Install Visual C++ 2015 Build Tools
- `$ heroku plugins:install heroku-kafka` wins

He also suggested that if we include windows-build-tools in the plugin (ideally only on Windows), that could avoid the "install node" step. We'd still need to install Python, .NET, and the VC++ build tools.

This is still pretty gross, so we should probably consider one of the solutions I suggested in https://github.com/heroku/herokudata/issues/409

[msakrejda]

Also Windows is EOL in 2020 and only getting security updates now; this may all be different on Windows 10 =D