fix(uiSelectNoChoice): support Selectize theme

Partial fix for #1608
Closes #1692

Author: gritchou

Diff for: src/selectize/no-choice.tpl.html

@@ -0,0 +1,6 @@
+<div class="ui-select-no-choice selectize-dropdown"
+    ng-show="$select.items.length == 0">
+    <div class="selectize-dropdown-content">
+        <div data-selectable="" ng-transclude></div>
+    </div>
+</div>

Diff for: src/selectize/select.tpl.html

@@ -13,4 +13,5 @@
            aria-label="{{ $select.baseTitle }}">
   </div>
   <div class="ui-select-choices"></div>
+  <div class="ui-select-no-choice"></div>
 </div>