search input always shows, even when disabled, if theme is set globally

Bug description:

if theme is set globally, search input still shows up even with search-enabled set to false. this is due to the CSS trying to select based on a theme attr that does not exist when the theme is set globally via uiSelectConfig.theme ... EG .ui-select-container[theme="selectize"]

Link to minimally-working plunker that reproduces the issue:

http://plnkr.co/edit/LslPFmp5DFKQ37hdQrMm?p=preview

Version of Angular, UI-Select, and Bootstrap/Select2/Selectize CSS

Angular: 1.5

UI-Select: 0.19.1

Bootstrap/Select2/Selectize CSS (if applicable): all

[user378230]

@ericdecarli This should be fairly easy to fix

1. Edit common.css
2. remove the .ui-select-container[theme="xxx"]
3. Replace with .ui-select-xxx
4. Update the select(-multiple).tpl.html files for select2/selectize

Can you submit a PR?