Updated plugin readme to mention WP8
Updated plugin readme to mention WP8

gbenvenuti/cordova-plugin-screen-orientation,SidneyS/cordova-plugin-screen-orientation,cristoferdomingues/cordova-plugin-screen-orientation,uygn/cordova-plugin-screen-orientation,SidneyS/cordova-plugin-screen-orientation,cristoferdomingues/cordova-plugin-screen-orientation,uygn/cordova-plugin-screen-orientation,kitmaxdevelop/cordova-plugin-screen-orientation,gbenvenuti/cordova-plugin-screen-orientation,gbenvenuti/cordova-plugin-screen-orientation,SidneyS/cordova-plugin-screen-orientation,kitmaxdevelop/cordova-plugin-screen-orientation,cristoferdomingues/cordova-plugin-screen-orientation,uygn/cordova-plugin-screen-orientation,kitmaxdevelop/cordova-plugin-screen-orientation