Fix Windows dev install

[mjadobson]

There were a few errors thrown when trying to set up Slate dev on Windows 10.

This pull request alters the npm scripts so that they will work cross platform. Additionally, it adds a note that windows-build-tools may be required before attempting to install.

[erquhart]

@mjadobson CI build is failing - you'll need to call the mkdirp binary directly. Example:

"build": "./node_modules/mkdirp/bin/cmd.js ./tmp && ..."

Otherwise it seems to work great - awesome improvement!

[mjadobson]

That's interesting. Do you know why that's the case? I thought it would have installed the devDeps and been able to run them like it's doing with eslint/browserify/etc

[erquhart]

Yeah that does make sense. Might be yarn, checking.

[erquhart]

Yep, it's yarn. Very strange. This seems related, not sure it applies to direct dependencies: yarnpkg/yarn#760.

It's only affecting mkdirp in this case. Might be yarn mishandling bin when defined as a path instead of an object (npm-run-all, eslint, and browserify binaries are all mapped out in objects, for example). Seems hitting the bin directly is necessary for now since this project uses yarn.

[brendancarney]

Closing, as this looks pretty out of date now. If there are still Windows issues, please feel free to update the PR or create an issue. Thanks!