move traverseSubviews method to SVGNode

ios/Elements/RNSVGDefs.m

@@ -13,11 +13,10 @@
 
 - (void)renderTo:(CGContextRef)context
 {
-    for (RNSVGNode *node in self.subviews) {
-        if ([node isKindOfClass:[RNSVGNode class]]) {
-            [node saveDefinition];
-        }
-    }
+    [self traverseSubviews:^(RNSVGNode *node) {
+        [node saveDefinition];
+        return YES;
+    }];
 }
 
 - (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event

ios/Elements/RNSVGGroup.m

@@ -99,16 +99,5 @@
     }];
 }
 
-- (void)traverseSubviews:(BOOL (^)(RNSVGNode *node))block
-{
-    for (RNSVGNode *node in self.subviews) {
-        if ([node isKindOfClass:[RNSVGNode class]]) {
-            if (!block(node)) {
-                break;
-            }
-        }
-    }
-}
-
 
 @end

ios/RNSVGNode.h

@@ -78,4 +78,6 @@
 
 - (void)endTransparencyLayer:(CGContextRef)context;
 
+- (void)traverseSubviews:(BOOL (^)(RNSVGNode *node))block;
+
 @end

ios/RNSVGNode.m

@@ -191,6 +191,17 @@
     // abstract
 }
 
+- (void)traverseSubviews:(BOOL (^)(RNSVGNode *node))block
+{
+    for (RNSVGNode *node in self.subviews) {
+        if ([node isKindOfClass:[RNSVGNode class]]) {
+            if (!block(node)) {
+                break;
+            }
+        }
+    }
+}
+
 - (void)resetProperties
 {
     // abstract