add _rxr_onPageDestroy() method to notify that RXRViewController is released
add _rxr_onPageDestroy() method to notify that RXRViewController is released

bigyelow/rexxar-ios,bigyelow/rexxar-ios,douban/rexxar-ios,daydayfree/rexxar-ios,bigyelow/rexxar-ios,daydayfree/rexxar-ios,douban/rexxar-ios,douban/rexxar-ios,daydayfree/rexxar-ios