#229: writing preview
#229: change the tab name and remove unnecessary dependency
#229: change http method in order to fix markdown bug
#229: remove unnecessary lines
#229: add unit tests and functional test and improve codes
#229: refactor previewing functionality's js parts
add spotlight icon to homepage.
Merge branch 'feature/229-preview-text' of git://github.com/windduke/19wu into windduke-feature/229-preview-text
#229: writing preview
#229: change the tab name and remove unnecessary dependency
#229: change http method in order to fix markdown bug
#229: remove unnecessary lines
#229: add unit tests and functional test and improve codes
#229: refactor previewing functionality's js parts
#229: refactor the markdown filter method by using registered filters
Merge pull request #242 from saberma/saberma-enhancement/add-spotlight-icon-to-homepage

首页显示三个特色大图标
add nav bottom border, use registered pipeline to render content. #241
merge.
Merge branch 'master' of github.com:saberma/19wu
use carrierwave host parameter.