Callback added in stop() and 'speed' property renamed to 'velocity'

src/wp8/BackgroundGeoLocation.cs

@@ -148,6 +148,7 @@ namespace Cordova.Extension.Commands
         {
             RunningInBackground = false;
             StopGeolocatorIfActive();
+            DispatchCommandResult(new PluginResult(PluginResult.Status.OK));
         }
 
         private void StopGeolocatorIfActive()

src/wp8/ExtensionMethods.cs

@@ -19,7 +19,7 @@ namespace Cordova.Extension.Commands
                                  "\"altitude\": {3}," +
                                  "\"altitudeAccuracy\": {4}," +
                                  "\"heading\": {5}," +
-                                 "\"speed\": {6}," +
+                                 "\"velocity\": {6}," +
                                  "\"timestamp\": {7}" +
                                  "}}"
                 , geocoordinate.Accuracy.ToString(numberFormatInfo)