fix close popover on tab issue in DatePicker

Author: ivansfdc

components/SLDSPicklistBase/index.jsx

@@ -182,6 +182,7 @@ module.exports = React.createClass( {
         <SLDSPopover 
           className='slds-dropdown slds-dropdown--left slds-dropdown--small slds-dropdown--menu' 
           targetElement={this.refs.date} 
+          closeOnTabKey={true}
           onClose={this.handleCancel}>
           {this.getPopoverContent()}
         </SLDSPopover>:null

components/SLDSPopover.js

@@ -36,8 +36,9 @@ module.exports = React.createClass( {
 
   getDefaultProps () {
     return {
-      targetAttachment: "bottom left",
-      className: "slds-dropdown"
+      targetAttachment: 'bottom left',
+      className: 'slds-dropdown',
+      closeOnTabKey: false 
     };
   },
 
@@ -73,8 +74,10 @@ module.exports = React.createClass( {
 
   handleKeyDown (event) {
     if(event.keyCode === KEYS.TAB){
-      EventUtil.trap(event);
-      this.handleClose();
+      if(this.props.closeOnTabKey){
+        EventUtil.trap(event);
+        this.handleClose();
+      }
     }
   },