added APPIUM_VERSION MobileCapabilityType

Author: Jonahss

src/main/java/io/appium/java_client/remote/MobileCapabilityType.java

@@ -21,4 +21,7 @@ public interface MobileCapabilityType extends CapabilityType {
  String APP_WAIT_ACTIVITY = "appWaitActivity";
  String APP_WAIT_PACKAGE = "appWaitPackage";
  String SELENDROID_PORT = "selendroidPort";
+
+ //Sauce-specific
+ String APPIUM_VERSION = "appiumVersion";
 }