Use postcss for compress

[tavriaforever]

Resolved #71
@blond
Not use clean-css because:

• removed sourcemap comment in bundle.css (can work only if building sourcemap by cleancss Don't remove source maps comments clean-css/clean-css#231)
• synchronous (it`s not big problem, but...)
• cssnano more consistent and understandable decision
• highly configurable and modular

Updated:
After a detailed study and discussion, the team decided to use the lesser evil and take csswring

[blond]

👎 All these problems far less evil than the difference between instruments.

It has been a lot of edits for use clean-css in islands.

/сс @tadatuta @arikon

[tavriaforever]

1. Now islands compressing their css by borschik + clean-css.
2. clean-css not compatible with sourcemap option
3. In part of cases cssnano better compressed css

I saw only one problem, that cssnano much slower than clean-css

[tavriaforever]

Send PR to bench module GoalSmashers/css-minification-benchmark#42

[arikon]

@blond @tavriaforever I'm not sure what to use =(

[tavriaforever]

@blond update PR

[blond]

Почему не склеить через массив? И почему тут нету переносов строк?

[tavriaforever]

Переносов строк нет, согласен, лучше добавить. Что касается массива не знаю почему решил так написать, если принципиально, могу переделать с массивом.