feat: support for windows

[Fonger]

Resolves #2

1. In windows, use powershell to download mongodb and unzip it.
   Maybe we can use builtin node.js module to download and use unzip package to keep the code clean?
2. To maintain compatibility with Windows 7, it does not use Expand-Archive to unzip the file because it's only available since PowerShell v5 (Windows 10)
3. mkdir -p in unix equals to mkdir or md in windows. However in Windows, mkdir an existing directory will throw error. So it checks if the path exists before creating one. (ignoring race condition)
4. Checking for every directory is redundant so I declare ports array for primary/secondary ports.

Tested on Windows 10.

[Fonger]

@vkarpov15 I forget to update README.md and remove Windows is not supported

run-rs/README.md

Lines 33 to 35 in 5e95c69

	## OS Support
	Run-rs supports Linux and OSX. Windows is **not** currently supported.

And for mongodb 4.1.x, it seems the filename becomes mongodb-win32-x86_64-2012plus-${version}.zip.

It's not released so I didn't handle this case. It's highly possible that when 4.2 is officially out, it will follow this new pattern.

[vkarpov15]

@Fonger I changed the run-rs README, thanks for the reminder. Re: 4.1.x, let's not worry about that yet, 4.1 is a dev-only release, we'll figure that out once 4.2 lands.