fix(tagging): infite digest loops when name is similar

Resolves issue where isDisabled was running for tags and causing a
infite loop to occur if the new tag value included a previous value.

For example:
  tag1: "a"
  tag2: "aa"

Fixes #1693

src/uiSelectController.js

@@ -351,6 +351,8 @@ uis.controller('uiSelectCtrl',
 
     if (itemIndex >= 0 && (angular.isDefined(ctrl.disableChoiceExpression) || ctrl.multiple)) {
 
+      if (item.isTag) return false;
+
       if (ctrl.multiple) {
         isDisabled = _isItemSelected(item);
       }