Fix readme

Author: kevinzhow

README.md

@@ -95,6 +95,25 @@ circleChart.backgroundColor = [UIColor clearColor];
 
 ```
 
+
+[![]([https://dl.dropboxusercontent.com/u/1599662/pie.png])]([https://dl.dropboxusercontent.com/u/1599662/pie.png])
+
+```objective-c
+# import "PNChart.h"
+//For PieChart
+NSArray *items = @[[PNPieChartDataItem dataItemWithValue:10 color:PNRed],
+                           [PNPieChartDataItem dataItemWithValue:20 color:PNBlue description:@"WWDC"],
+                           [PNPieChartDataItem dataItemWithValue:40 color:PNGreen description:@"GOOL I/O"],
+                           ];
+        
+        
+        
+PNPieChart *pieChart = [[PNPieChart alloc] initWithFrame:CGRectMake(40.0, 155.0, 240.0, 240.0) items:items];
+pieChart.descriptionTextColor = [UIColor whiteColor];
+pieChart.descriptionTextFont  = [UIFont fontWithName:@"Avenir-Medium" size:14.0];
+[pieChart strokeChart];
+```
+
 #### Callback
 
 Currently callback only works on Linechart