Single tviz UI fix

client/views/app.html

@@ -40,10 +40,12 @@
 
 <div class="row">
     <div class="col-md-6">
-        <div id="tvizAnd"></div>
+        <h1>And operator</h1>
+        <div id="tvizAnd" class="text-center"></div>
     </div>
     <div class="col-md-6">
-        <div id="tvizAverage"></div>
+        <h1>Average operator</h1>
+        <div id="tvizAverage" class="text-center"></div>
     </div>
 </div>