fix(tabs): adding bootstrap 4 specific class

Author: uxtx

Diff for: src/tabs/test/tabs.spec.js

@@ -56,6 +56,10 @@ describe('tabs', function() {
     it('should pass class and other attributes on to tab template', function() {
       expect(elm).toHaveClass('hello');
       expect(elm.attr('data-pizza')).toBe('pepperoni');
+      // ensure that we have our bootstrap 4 link prefix so things are future
+      // proofed.
+      var link  = $(elm.find('a')[0]);
+      expect(link).toHaveClass('nav-link');
     });
 
     it('should create clickable titles', function() {

Diff for: template/tabs/tab.html

@@ -1,3 +1,3 @@
-<li ng-class="{active: active, disabled: disabled}" class="uib-tab">
-  <a href ng-click="select()" uib-tab-heading-transclude>{{heading}}</a>
+<li ng-class="{active: active, disabled: disabled}" class="uib-tab nav-item">
+  <a href ng-click="select()" class="nav-link" uib-tab-heading-transclude>{{heading}}</a>
 </li>