[Flow] Properly fix new errors as of Flow v0.10.

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.';

Examples/UIExplorer/UIExplorerList.js

@@ -11,7 +11,7 @@
  * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  *
- * --flow disabled--
+ * @flow
  */
 'use strict';
 

Libraries/Components/TabBarIOS/TabBarItemIOS.ios.js

@@ -89,7 +89,7 @@ var TabBarItemIOS = React.createClass({
     }
   },
 
-  componentWillReceiveProps: function(nextProps: { selected: any /* workaround for flow bug */ }) {
+  componentWillReceiveProps: function(nextProps: { selected?: boolean }) {
     if (this.state.hasBeenSelected || nextProps.selected) {
       this.setState({hasBeenSelected: true});
     }