Clean the errors that Flow v0.10.0 finds

Examples/UIExplorer/ActivityIndicatorIOSExample.js

@@ -57,6 +57,7 @@ var ToggleAnimatingActivityIndicator = React.createClass({
   }
 });
 
+exports.displayName = (undefined: ?string);
 exports.framework = 'React';
 exports.title = '<ActivityIndicatorIOS>';
 exports.description = 'Animated loading indicators.';

Libraries/Components/TabBarIOS/TabBarItemIOS.ios.js

@@ -86,7 +86,7 @@ var TabBarItemIOS = React.createClass({
     }
   },
 
-  componentWillReceiveProps: function(nextProps: { selected: boolean }) {
+  componentWillReceiveProps: function(nextProps: { selected?: boolean }) {
     if (this.state.hasBeenSelected || nextProps.selected) {
       this.setState({hasBeenSelected: true});
     }

Libraries/ReactIOS/ReactIOSMount.js

@@ -194,7 +194,7 @@ var ReactIOSMount = {
   unmountComponentAtNode: function(containerTag: number): bool {
     if (!ReactIOSTagHandles.reactTagIsNativeTopRootID(containerTag)) {
       console.error('You cannot render into anything but a top root');
-      return;
+      return false;
     }
 
     var containerID = ReactIOSTagHandles.tagToRootNodeID[containerTag];