modal docs: ensure all <button>s have an explicit `type` attribute

[skip sauce]

docs/_includes/js/modal.html

@@ -102,13 +102,13 @@
   </div><!-- /.modal -->
 
   <div class="bs-example" style="padding-bottom: 24px;">
-    <button class="btn btn-primary btn-lg" data-toggle="modal" data-target="#myModal">
+    <button type="button" class="btn btn-primary btn-lg" data-toggle="modal" data-target="#myModal">
       Launch demo modal
     </button>
   </div><!-- /example -->
 {% highlight html %}
 <!-- Button trigger modal -->
-<button class="btn btn-primary btn-lg" data-toggle="modal" data-target="#myModal">
+<button type="button" class="btn btn-primary btn-lg" data-toggle="modal" data-target="#myModal">
   Launch demo modal
 </button>
 
@@ -146,12 +146,12 @@
   <h2 id="modals-sizes">Optional sizes</h2>
   <p>Modals have two optional sizes, available via modifier classes to be placed on a <code>.modal-dialog</code>.</p>
   <div class="bs-example">
-    <button class="btn btn-primary" data-toggle="modal" data-target=".bs-example-modal-lg">Large modal</button>
-    <button class="btn btn-primary" data-toggle="modal" data-target=".bs-example-modal-sm">Small modal</button>
+    <button type="button" class="btn btn-primary" data-toggle="modal" data-target=".bs-example-modal-lg">Large modal</button>
+    <button type="button" class="btn btn-primary" data-toggle="modal" data-target=".bs-example-modal-sm">Small modal</button>
   </div>
 {% highlight html %}
 <!-- Large modal -->
-<button class="btn btn-primary" data-toggle="modal" data-target=".bs-example-modal-lg">Large modal</button>
+<button type="button" class="btn btn-primary" data-toggle="modal" data-target=".bs-example-modal-lg">Large modal</button>
 
 <div class="modal fade bs-example-modal-lg" tabindex="-1" role="dialog" aria-labelledby="myLargeModalLabel" aria-hidden="true">
   <div class="modal-dialog modal-lg">
@@ -162,7 +162,7 @@
 </div>
 
 <!-- Small modal -->
-<button class="btn btn-primary" data-toggle="modal" data-target=".bs-example-modal-sm">Small modal</button>
+<button type="button" class="btn btn-primary" data-toggle="modal" data-target=".bs-example-modal-sm">Small modal</button>
 
 <div class="modal fade bs-example-modal-sm" tabindex="-1" role="dialog" aria-labelledby="mySmallModalLabel" aria-hidden="true">
   <div class="modal-dialog modal-sm">