Added a code for supporting storyboard or nib.
Added a code for supporting storyboard or nib.

TimorCan/NJKWebViewProgress,jianwoo/NJKWebViewProgress,phaibin/NJKWebViewProgress,zhouwude/NJKWebViewProgress,liuruxian/NJKWebViewProgress,vvw/NJKWebViewProgress,zhaoguohui/NJKWebViewProgress,AbooJan/NJKWebViewProgress,linxiaoguo/NJKWebViewProgress,xb123456456/NJKWebViewProgress,XuXiaoJunChina/NJKWebViewProgress,hanhailong/NJKWebViewProgress,Suninus/NJKWebViewProgress,ninjinkun/NJKWebViewProgress,bboyesc/NJKWebViewProgress