Support stdin, stdout

[btubbs]

It would be a lot easier to use inky-cli in my Makefile if it could accept input on stdin, and print output to stdout. As it is, I'm going to have to create temporary files in between inky processing and CSS inlining.

(I know you have your own pipeline of Grunt tasks, but I don't want to use Grunt.)

A common CLI pattern is to use a dash ("-") as the filename argument to signal that input should be read from stdin instead of a file, or be printed to stdout instead of a file. Could inky-cli do that?

[rclmenezes]

For now, I made a handy dandy script:

const Inky = require('inky').Inky;
const cheerio = require('cheerio');
const getStdin = require('get-stdin');

const options = {};
const inky = new Inky(options);
getStdin().then(input => {
    const html = cheerio.load(input);
    const convertedHtml = inky.releaseTheKraken(html);
    console.log(convertedHtml);
});