Allows the config file to return a Promise

[gitgrimbo]

Allows the config file to return a Promise.

The change basically wraps bin/cli.js in an async function and awaits the result of calling loadConfig().

---

Sample command:

replace-in-file --configFile=replace-in-file.config.js

Sample replace-in-file.config.js file:

const simplegit = require("simple-git/promise");
const git = simplegit();

async function latestVersion() {
  const opts = {
    // latest single entry
    "-1": null,
  };
  const log = await git.log(opts);
  const { latest } = log;
  return latest.hash.substring(0, 8);
}

async function makeConfig() {
  const codeVersion = await latestVersion();
  return {
    files: "public/**/*",
    from: /@CODE_VERSION@/g,
    to: codeVersion,
  };
}

module.exports = makeConfig();

[coveralls]

Coverage remained the same at 100.0% when pulling 68558c3 on gitgrimbo:async-config into f94e466 on adamreisnz:master.