Name the 'appVersion' parameter consistently

Author: Richard Hua

ios/CodePush/CodePush.h

@@ -34,7 +34,7 @@
  * to be specified, which would otherwise default to the
  * App Store version of the app.
  */
-+ (void)overrideAppVersion:(NSString *)deploymentKey;
++ (void)overrideAppVersion:(NSString *)appVersion;
 
 /*
  * This method allows dynamically setting the app's
@@ -167,4 +167,4 @@ typedef NS_ENUM(NSInteger, CodePushUpdateState) {
     CodePushUpdateStateRunning,
     CodePushUpdateStatePending,
     CodePushUpdateStateLatest
-};
+};