docs(tutorial/step_03): sync markup with angular-phonecat

Update from Bootstrap 2.3 to 3.1 changed "span" to "col" tags

Closes #7172

Author: ttam3d0

docs/content/tutorial/step_03.ngdoc

@@ -28,14 +28,14 @@ __`app/index.html`:__
 
 ```html
   <div class="container-fluid">
-    <div class="row-fluid">
-      <div class="span2">
+    <div class="row">
+      <div class="col-md-2">
         <!--Sidebar content-->
 
         Search: <input ng-model="query">
 
       </div>
-      <div class="span10">
+      <div class="col-md-10">
         <!--Body content-->
 
         <ul class="phones">