Fix nested SafeAreaViews (#84)

On iOS, nested safe area views do not get their padding applied. I think this is because `setSafeAreaInsets` overrides the existing selector - but we don't need to do that as we have `safeAreaInsetsDidChange`

This simplifies the logic a bit too

ios/SafeAreaView/RNCSafeAreaView.m

@@ -45,14 +45,10 @@ - (NSString *)description
 
 - (void)safeAreaInsetsDidChange
 {
+  [super safeAreaInsetsDidChange];
   [self invalidateSafeAreaInsets];
 }
 
-- (void)invalidateSafeAreaInsets
-{
-  [self setSafeAreaInsets:[self realOrEmulateSafeAreaInsets:self.emulateUnlessSupported]];
-}
-
 - (void)layoutSubviews
 {
   [super layoutSubviews];
@@ -62,15 +58,10 @@ - (void)layoutSubviews
   }
 }
 
-- (void)updateLocalData
+- (void)invalidateSafeAreaInsets
 {
-  RNCSafeAreaViewLocalData *localData = [[RNCSafeAreaViewLocalData alloc] initWithInsets:_currentSafeAreaInsets
-                                                                                   edges:_edges];
-  [_bridge.uiManager setLocalData:localData forView:self];
-}
+  UIEdgeInsets safeAreaInsets = [self realOrEmulateSafeAreaInsets:self.emulateUnlessSupported];
 
-- (void)setSafeAreaInsets:(UIEdgeInsets)safeAreaInsets
-{
   if (UIEdgeInsetsEqualToEdgeInsetsWithThreshold(safeAreaInsets, _currentSafeAreaInsets, 1.0 / RCTScreenScale())) {
     return;
   }
@@ -79,6 +70,13 @@ - (void)setSafeAreaInsets:(UIEdgeInsets)safeAreaInsets
   [self updateLocalData];
 }
 
+- (void)updateLocalData
+{
+  RNCSafeAreaViewLocalData *localData = [[RNCSafeAreaViewLocalData alloc] initWithInsets:_currentSafeAreaInsets
+                                                                                   edges:_edges];
+  [_bridge.uiManager setLocalData:localData forView:self];
+}
+
 - (void)setEmulateUnlessSupported:(BOOL)emulateUnlessSupported
 {
   if (_emulateUnlessSupported == emulateUnlessSupported) {