Option groups

[just-boris]

I like this lib, it's good replacement to select2 in angular projects. Now there is lacks only list grouping which exists in native select and select2. I see your plans on it in your roadmap and I suggest to discuss future feature api here.
I propose the new keyword in repeat option — group by, like it used in angular select directive in ng-options attribute:

<ui-select ng-model="person.selected" theme="select2" class="form-control">
    <match placeholder="Select or search a person in the list...">{{$select.selected.name}}</match>
    <choices repeat="group by item.department for item in people">
        <span ng-bind-html="item.name | highlight: $select.search"></span>
        <small ng-bind-html="item.email | highlight: $select.search"></small>
    </choices>
</ui-select>

I can try implement this feature, if you approve this grouping definition