demo(datepicker): add type attribute to buttons

Closes #1890
Closes #1894

Author: bekos

Diff for: src/datepicker/docs/demo.html

@@ -12,7 +12,7 @@ <h4>Popup</h4>
             <p class="input-group">
               <input type="text" class="form-control" datepicker-popup="{{format}}" ng-model="dt" is-open="opened" min-date="minDate" max-date="'2015-06-22'" datepicker-options="dateOptions" date-disabled="disabled(date, mode)" ng-required="true" close-text="Close" />
               <span class="input-group-btn">
-                <button class="btn btn-default" ng-click="open($event)"><i class="glyphicon glyphicon-calendar"></i></button>
+                <button type="button" class="btn btn-default" ng-click="open($event)"><i class="glyphicon glyphicon-calendar"></i></button>
               </span>
             </p>
         </div>
@@ -24,8 +24,8 @@ <h4>Popup</h4>
     </div>
 
     <hr />
-    <button class="btn btn-sm btn-info" ng-click="today()">Today</button>
-    <button class="btn btn-sm btn-default" ng-click="dt = '2009-08-24'">2009-08-24</button>
-    <button class="btn btn-sm btn-danger" ng-click="clear()">Clear</button>
-    <button class="btn btn-sm btn-default" ng-click="toggleMin()" tooltip="After today restriction">Min date</button>
+    <button type="button" class="btn btn-sm btn-info" ng-click="today()">Today</button>
+    <button type="button" class="btn btn-sm btn-default" ng-click="dt = '2009-08-24'">2009-08-24</button>
+    <button type="button" class="btn btn-sm btn-danger" ng-click="clear()">Clear</button>
+    <button type="button" class="btn btn-sm btn-default" ng-click="toggleMin()" tooltip="After today restriction">Min date</button>
 </div>