added build.gradle file for selendroid-standalone
added build.gradle file for selendroid-standalone

vishals79/appium-uiautomator2-driver,vishals79/appium-uiautomator2-driver,vishals79/appium-uiautomator2-driver,vishals79/appium-uiautomator2-driver,vishals79/appium-uiautomator2-driver