use correct spelling of aria-labelledby

see http://accessibleculture.org/articles/2011/03/its-spelled-aria-labelledby/

Author: lukfugl

lib/components/TabPanel.js

@@ -44,7 +44,7 @@ module.exports = React.createClass({
         )}
         role="tabpanel"
         id={this.props.id}
-        aria-labeledby={this.props.tabId}
+        aria-labelledby={this.props.tabId}
         style={{display: this.props.selected ? null : 'none'}}
       >
         {children}

lib/components/__tests__/TabPanel-test.js

@@ -12,7 +12,7 @@ describe('Tab', function() {
 
     equal(node.className, 'ReactTabs__TabPanel');
     equal(node.getAttribute('role'), 'tabpanel');
-    equal(node.getAttribute('aria-labeledby'), null);
+    equal(node.getAttribute('aria-labelledby'), null);
     equal(node.getAttribute('id'), null);
     equal(node.innerHTML, '');
     equal(node.style.display, 'none');
@@ -30,7 +30,7 @@ describe('Tab', function() {
     const node = findDOMNode(tabPanel);
 
     equal(node.className, 'ReactTabs__TabPanel ReactTabs__TabPanel--selected');
-    equal(node.getAttribute('aria-labeledby'), '1234');
+    equal(node.getAttribute('aria-labelledby'), '1234');
     equal(node.getAttribute('id'), 'abcd');
     equal(node.innerHTML, 'Hola');
     equal(node.style.display, '');

lib/components/__tests__/Tabs-test.js

@@ -93,7 +93,7 @@ describe('react-tabs', function() {
         equal(panel.getAttribute('role'), 'tabpanel');
 
         equal(tab.getAttribute('aria-controls'), panel.getAttribute('id'));
-        equal(panel.getAttribute('aria-labeledby'), tab.getAttribute('id'));
+        equal(panel.getAttribute('aria-labelledby'), tab.getAttribute('id'));
       }
 
       equal(findDOMNode(tabs.getTab(3)).getAttribute('aria-disabled'), 'true');