Process images on default gulp task.

Author: Marion Duprey

.gitignore

@@ -5,3 +5,4 @@ _site
 **/.DS_Store
 node_modules
 vendor
+assets

gulpfile.js

@@ -64,4 +64,4 @@ gulp.task('watch', function () {
  * Default task, running just `gulp` will compile the stylus,
  * compile the jekyll site, launch BrowserSync & watch files.
  */
-gulp.task('default', ['js', 'stylus', 'watch']);
+gulp.task('default', ['js', 'stylus', 'imagemin', 'watch']);