Automatically detect if Tailwind is installed with npm

[weaverryan]

If you have tailwindcss in your package.json, we should automatically detect and use that instead of downloading the binary. Just smooth out that workflow if the user wants to require tailwind via npm.

[bocharsky-bw]

@weaverryan Should we go further and check if tailwindcss is installed in the system locally? I see I can install it with brew install tailwindcss that I believe will give me tailwindcss global alias? Probably scopes would:

1. Check if it's in package.json
2. Or check if it's installed locally
3. Or download the bin ourselves.

or will it just confuse things?