Add docker support for dev

Gemfile

@@ -1,2 +1,6 @@
 source 'https://rubygems.org'
 gem 'github-pages'
+
+group :jekyll_plugins do
+    gem 'jekyll-livereload'
+end

docker-compose.yml

@@ -0,0 +1,8 @@
+jekyll:
+    image: graffen/jekyll
+    command: jekyll serve --livereload --reload_port 35729
+    ports:
+        - 4000:4000
+        - 35729:35729
+    volumes:
+        - .:/srv/jekyll

gulpfile.js

@@ -1,46 +0,0 @@
-var gulp        = require('gulp');
-var browserSync = require('browser-sync');
-var cp          = require('child_process');
-
-var messages = {
-    jekyllBuild: '<span style="color: grey">Running:</span> $ jekyll build'
-};
-
-/**
- * Build the Jekyll Site
- */
-gulp.task('jekyll-build', function (done) {
-    browserSync.notify(messages.jekyllBuild);
-    return cp.spawn('bundle', ['exec','jekyll','build'], {stdio: 'inherit'})
-        .on('close', done);
-});
-
-/**
- * Rebuild Jekyll & do page reload
- */
-gulp.task('jekyll-rebuild', ['jekyll-build'], function () {
-    browserSync.reload();
-});
-
-/**
- * Wait for jekyll-build, then launch the Server
- */
-gulp.task('browser-sync', ['jekyll-build'], function() {
-    browserSync.init({
-        server: '_site'
-    });
-});
-
-/**
- * Watch html/md files, run jekyll & reload BrowserSync
- * if you add folder for pages, collection or datas, add them to this list
- */
-gulp.task('watch', function () {
-    gulp.watch(['./*', '_layouts/*', 'assets/**/*', 'keysigning/*'], ['jekyll-rebuild']);
-});
-
-/**
- * Default task, running just `gulp` will compile the sass,
- * compile the jekyll site, launch BrowserSync & watch files.
- */
-gulp.task('default', ['browser-sync', 'watch']);