Browser sync

# Changelog
- Fixed PNG paths.
- Cleanup includes
- Added BrowserSync

# BrowserSync
Included BrowserSync to the workflow. You need to run `npm install` again to install the dependencies.
Added a new gulp-task `gulp watch-sync` to enable BrowserSync.

After running `gulp watch-sync` a new browser window will open and reloading at php changes and injecting css and js.

## Important
You need to setup a vhost for your webserver, which will be used as a proxy for BrowserSync.
Setup your vhost to `yolo.local` or change it in the `gulpfile.js`