Keep header comment on minify
Keep header comment on minify

Some minifier keep header comment over its format.

1. YUI Compressor
It keeps the header comments beggining with `/*!`
  * http://yui.github.io/yuicompressor/css.html#special-comments

2. Closure compiler
It keeps the header comments containing `@license` or `@preserve`
  * https://developers.google.com/closure/compiler/docs/js-for-compiler#tag-license

I think header comment is very important because it includes its own license.

iamdanfox/github,lucusp/github,yaoxiaoyong/github-1,teresakrause/github,jabez128/github,mushishi78/github,cassioscabral/github,aendrew/github,jenbennings/github,adjohnson916/github,yuya-takeyama/github,kidaa/github,mcanthony/github,github-tools/github,esironal/github,bankonme/github,cassioscabral/github,lukeburns/github,yorkie/github-1,w35l3y/github-js,michael/github,amenadiel/github,weflex/octop,sultanshakir/github,cassioscabral/github,michael/github,kustomzone/github,github-tools/github,arosenberg01/github,vmolsa/github,github-tools/github,baoshan/github,jedfoster/github,cmfcmf/github,w35l3y/github-js,michael/github,rschindlauer/github,petrosh/github,firehist/github,JensLincke/github