Try to use redoc-cli.
I was using bootprint-openapi by which I was generating a bunch of files (bundle.js, bundle.js.map, index.html, main.css and main.css.map) and then you can convert it into a single .html file using html-inline to generate a simple index.html file.
Then I found redoc-cli very easy to to use and output is really-2 awesome, a single and beautiful index.html file.
Installation:
npm install -g redoc-cli
Usage:
redoc-cli bundle -o index.html swagger.json