fix #2222 move default backgroundColor to initialize() as initWithCoder also needs it
fix #2222 move default backgroundColor to initialize() as initWithCoder also needs it

liuxuan30/Charts,liuxuan30/ios-charts,liuxuan30/Charts,danielgindi/Charts,danielgindi/Charts,FreddyZeng/Charts,SereivoanYong/Charts,danielgindi/ios-charts,liuxuan30/Charts,liuxuan30/Charts,jum/Charts,jjatie/Charts,hanquochan/Charts,MAARK/Charts,danielgindi/Charts,danielgindi/ios-charts,icecrystal23/ios-charts,MAARK/Charts,icecrystal23/ios-charts,MAARK/Charts,FreddyZeng/Charts,MAARK/Charts,liuxuan30/ios-charts,jum/Charts,danielgindi/ios-charts,jum/Charts,jjatie/Charts,hanquochan/Charts,ConcepterDev/ios-charts,FreddyZeng/Charts,icecrystal23/ios-charts,ConcepterDev/ios-charts,hanquochan/Charts,jum/Charts,ConcepterDev/ios-charts,danielgindi/Charts,jjatie/Charts,SereivoanYong/Charts,jjatie/Charts,SereivoanYong/Charts,liuxuan30/ios-charts,FreddyZeng/Charts,danielgindi/ios-charts,icecrystal23/ios-charts,hanquochan/Charts,liuxuan30/ios-charts