Gulp update

- Updates gulp version to 3.5.2
- Applies dependence in the browserfy, coffee and scripts tasks to make them run in sequence (https://github.com/adrrian17/webapp-stack/commit/832187c1fb7cce8da42987858d0cf1c6a454029e)
- Updates doctype in the layout.jade file, the new syntax is ```doctype html``` for HTML 5