fix(tabs): remove flex; bring ink into same parent as links (#3331)

src/lib/tabs/tab-nav-bar/tab-nav-bar.html

@@ -1,5 +1,5 @@
 <div class="mat-tab-links">
   <ng-content></ng-content>
+  <md-ink-bar></md-ink-bar>
 </div>
 
-<md-ink-bar></md-ink-bar>

src/lib/tabs/tab-nav-bar/tab-nav-bar.scss

@@ -7,13 +7,14 @@
 }
 
 .mat-tab-links {
-  display: flex;
   position: relative;
 }
 
 // Wraps each link in the header
 .mat-tab-link {
   @include tab-label;
+  display: inline-block;
+  vertical-align: top;
   text-decoration: none;  // Removes anchor underline styling
   position: relative;
   overflow: hidden;  // Keeps the ripple from extending outside the element bounds