Add rainy assets

Signed-off-by: poc7667 <poc7667@gmail.com>
Fix:avoid overflow li items, http://stackoverflow.com/questions/297251/html-css-li-wrapping
Merge branch 'hotfix/fix_nav_li_overflow'
Merge branch 'hotfix/fix_nav_li_overflow' into develop
Support rainy mode,  fix by z-index (see javascript)
Add rainny asset demo html
Merge branch 'feature/add_rain_effect' into develop
Merge branch 'develop'