Dropdown support for Appbar

[quanglam2807]

Correct the view of DropDownMenu in Appbar

var menuItems = [
   { payload: '1', text: 'Never' },
   { payload: '2', text: 'Every Night' },
   { payload: '3', text: 'Weeknights' },
   { payload: '4', text: 'Weekends' },
   { payload: '5', text: 'Weekly' },
];
var sectionList = (<DropDownMenu menuItems={menuItems} />);
<AppBar
        className="mui-dark-theme"
        showMenuIconButton={true}
        title={sectionList}
        zDepth={1}>
</AppBar>

[hai-cea]

@nhutquang97 I'm sorry this didn't get merged in before v0.8. Would you like to resubmit a PR?

[matias-sandell]

+1