Change readme info.
Change API namespace.

From `chrome.*` to `sogouExplorer.*`, as instructed by
http://ie.sogou.com/open/doc/?id=1_1&title=API%E5%88%B6%E5%AE%9A%E8%A7%84%E8%8C%83%E7%AE%80%E4%BB%8B