Added backButton.color support

lib/ios/RNNBackButtonOptions.h

 @property (nonatomic, strong) NSString* title;
 @property (nonatomic, strong) NSString* transition;
 @property (nonatomic, strong) NSNumber* showTitle;
+@property (nonatomic, strong) NSNumber* color;
 
 @end

lib/ios/RNNBackButtonOptions.m

 #import "RNNBackButtonOptions.h"
+#import "UIImage+tint.h"
 
 @implementation RNNBackButtonOptions
 
 - (void)applyOn:(UIViewController *)viewController {
 	if (self.icon) {
-		UIImage *image = self.icon ? [RCTConvert UIImage:self.icon] : nil;
-		[viewController.navigationController.navigationBar setBackIndicatorImage:image];
-		[viewController.navigationController.navigationBar setBackIndicatorTransitionMaskImage:image];
+		UIImage *image = self.tintedIcon;
+		[viewController.navigationController.navigationBar setBackIndicatorImage:[UIImage new]];
+		[viewController.navigationController.navigationBar setBackIndicatorTransitionMaskImage:[UIImage new]];
+		
+		UIBarButtonItem *backItem = [[UIBarButtonItem alloc] initWithImage:image style:UIBarButtonItemStylePlain target:nil action:nil];
+		viewController.navigationItem.backBarButtonItem = backItem;
+	} else if (self.title) {
+		UIBarButtonItem *backItem = [[UIBarButtonItem alloc] initWithTitle:self.title
+																	 style:UIBarButtonItemStylePlain
+																	target:nil
+																	action:nil];
+		
+		viewController.navigationItem.backBarButtonItem = backItem;
 	}
 	
 	if (self.visible) {
 	if (self.showTitle && ![self.showTitle boolValue]) {
 		self.title = @"";
 	}
-	
-	if (self.title) {
-		UIBarButtonItem *backItem = [[UIBarButtonItem alloc] initWithTitle:self.title
-																	 style:UIBarButtonItemStylePlain
-																	target:nil
-																	action:nil];
-		
-		viewController.navigationItem.backBarButtonItem = backItem;
+}
+
+- (UIImage *)tintedIcon {
+	UIImage *image = self.icon ? [RCTConvert UIImage:self.icon] : nil;
+	if (self.color) {
+		return [[image withTintColor:[RCTConvert UIColor:self.color]] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
 	}
+	
+	return image;
 }
 
 @end

lib/ios/RNNTitleOptions.m

 	}
 	
 	NSDictionary* fontAttributes = [self fontAttributes];
-	
+
 	if (fontAttributes.allKeys.count > 0) {
 		viewController.navigationController.navigationBar.titleTextAttributes = fontAttributes;
 	}
 			if (self.fontSize) {
 				navigationBarTitleTextAttributes[NSFontAttributeName] = [UIFont fontWithName:self.fontFamily size:[self.fontSize floatValue]];
 			} else {
-				navigationBarTitleTextAttributes[NSFontAttributeName] = [UIFont fontWithName:self.fontFamily size:20];
+				navigationBarTitleTextAttributes[NSFontAttributeName] = [UIFont fontWithName:self.fontFamily size:17];
 			}
 		} else if (self.fontSize) {
 			navigationBarTitleTextAttributes[NSFontAttributeName] = [UIFont systemFontOfSize:[self.fontSize floatValue]];

lib/ios/RNNTopBarOptions.m

 		viewController.navigationController.hidesBarsOnSwipe = NO;
 	}
 	
-	if (self.buttonColor) {
-		UIColor* buttonColor = [RCTConvert UIColor:self.buttonColor];
-		viewController.navigationController.navigationBar.tintColor = buttonColor;
-	} else {
-		viewController.navigationController.navigationBar.tintColor = nil;
-	}
-	
 	if ([self.blur boolValue]) {
 		if (![viewController.navigationController.navigationBar viewWithTag:BLUR_TOPBAR_TAG]) {