Adding <select multiple> styles

I am using Gumby in a new project and while updating HTML elements such as radio buttons, check boxes, and select elements I found that multi selects were not part of the Gumby UI demo.  I checked the CSS files and found no styling other than '.picker select'.  Prefacing the <select> elements with the 'picker' class triggers Gumby's design updates to the select (making multi-selects appear like drop down selects) so instead I think a new class of 'multi-picker' could help and be used as the wrapper for multi-selects instead of 'picker'.

Select "Picker" Example:
<div class="picker">
    <select>
        <option value="#" disabled="">Favorite Dalek phrase...</option>
        <option>EXTERMINATE</option>
        <option>EXTERMINATE</option>
        <option>EXTERMINATE</option>
    </select>
</div>

Select "Multi-Picker" Example:
<div class="multi-picker">
    <select multiple="multiple">
        <option value="#" disabled="">Favorite Dalek phrase...</option>
        <option>EXTERMINATE</option>
        <option>EXTERMINATE</option>
        <option>EXTERMINATE</option>
    </select>
</div>

The proposed styles attempt to use many of the same styles already used in Gumby's UI for <select> differing only where needed such as background-image/color, padding, etc.