Merge pull request #294 from cwwise/patch-1

修改隐藏和显示 NavigationBar方法，让过度动画更加自然

TZImagePickerController/TZImagePickerController/TZPhotoPreviewController.m

@@ -63,7 +63,7 @@
 
 - (void)viewWillAppear:(BOOL)animated {
     [super viewWillAppear:animated];
-    [self.navigationController setNavigationBarHidden:YES];
+    [self.navigationController setNavigationBarHidden:YES animated:YES];
     if (iOS7Later) [UIApplication sharedApplication].statusBarHidden = YES;
     if (_currentIndex) [_collectionView setContentOffset:CGPointMake((self.view.tz_width + 20) * _currentIndex, 0) animated:NO];
     [self refreshNaviBarAndBottomBarState];
@@ -71,7 +71,7 @@
 
 - (void)viewWillDisappear:(BOOL)animated {
     [super viewWillDisappear:animated];
-    [self.navigationController setNavigationBarHidden:NO];
+    [self.navigationController setNavigationBarHidden:NO animated:YES];
     if (iOS7Later) [UIApplication sharedApplication].statusBarHidden = NO;
     [TZImageManager manager].shouldFixOrientation = NO;
 }