Merge pull request #5 from RubyLouvre/master

merge from RubyLouvre/onionui
构造option
Merge branch 'master' of https://github.com/RubyLouvre/avalon.oniui
update dropdown的数据匹配
增加multiple dropdown的例子
Merge branch 'master' of https://github.com/RubyLouvre/avalon.oniui
Merge pull request #40 from ilife5/master

完成dropdown menu部分，增加相应的例子