add buttons to input groups on test

tests/components.html

@@ -1327,16 +1327,25 @@
           <div class="input-group">
             <span class="input-group-addon input-lg">@</span>
             <input type="text" class="form-control input-lg" placeholder="Username">
+            <span class="input-group-btn">
+              <button class="btn btn-default btn-lg" type="button">Go!</button>
+            </span>
           </div>
           <br>
           <div class="input-group">
             <span class="input-group-addon">@</span>
             <input type="text" class="form-control" placeholder="Username">
+            <span class="input-group-btn">
+              <button class="btn btn-default" type="button">Go!</button>
+            </span>
           </div>
           <br>
           <div class="input-group">
             <span class="input-group-addon input-sm">@</span>
             <input type="text" class="form-control input-sm" placeholder="Username">
+            <span class="input-group-btn">
+              <button class="btn btn-default btn-sm" type="button">Go!</button>
+            </span>
           </div>
         </form>