Jekyll CSS Hot Reloading with Browsersync

gulpfile.js

var gulp        = require('gulp');
var changed     = require('gulp-changed-in-place');
var browserSync = require('browser-sync').create();

gulp.task('watch', ['css'], function() {
  browserSync.init({
    server: "./_site"
  });

  gulp.watch("_site/css/**/*.css", ['css']);
});

gulp.task('css', function() {
  return gulp.src("_site/css/**/*.css")
    .pipe(changed())
    .pipe(browserSync.stream());
});

package.json

{
  "name": "example.com",
  "version": "1.0.0",
  "devDependencies": {
    "browser-sync": "^2.18.13",
    "gulp": "^3.9.1",
    "gulp-changed-in-place": "^2.3.0",
    "parallelshell": "^3.0.1"
  },
  "scripts": {
    "watch": "parallelshell 'bundle exec jekyll build --watch' 'gulp watch'"
  }
}