Make dataSource visible in IB

Author: Denis Lebedev

Source/BarGraph/GKBarGraph.h

@@ -32,7 +32,7 @@
 @property (nonatomic, assign) BOOL animated;
 @property (nonatomic, assign) CFTimeInterval animationDuration;
 
-@property (nonatomic, assign) id<GKBarGraphDataSource> dataSource;
+@property (nonatomic, weak) IBOutlet id<GKBarGraphDataSource> dataSource;
 
 @property (nonatomic, strong) NSArray *bars;
 @property (nonatomic, strong) NSArray *labels;

Source/LineGraph/GKLineGraph.h

@@ -32,7 +32,7 @@
 @property (nonatomic, assign) BOOL animated;
 @property (nonatomic, assign) CFTimeInterval animationDuration;
 
-@property (nonatomic, assign) id<GKLineGraphDataSource> dataSource;
+@property (nonatomic, weak) IBOutlet id<GKLineGraphDataSource> dataSource;
 
 @property (nonatomic, assign) CGFloat lineWidth;
 @property (nonatomic, assign) CGFloat margin;