Release 3.0.2

- added BEM naming conventions
- added a guideline to use ``js-`` prefix for javascript functionality
- added z-index function helper
- changed structure of ``layout/_mixins.scss``
- changed sass file heading end ending comments to be more descriptive
- removed compress as dependency

The removal of compress was required as Aldryn now supports Google PageSpeed automation. This means we'd have to implement it manually again on local projects.