Added simple README
Added simple README

appnexus/mobile-sdk-ios,appnexus/mobile-sdk-ios,appnexus/mobile-sdk-ios,8tracks/appnexus-mobile-sdk-ios,appnexus/mobile-sdk-ios,8tracks/appnexus-mobile-sdk-ios,appnexus/mobile-sdk-ios,8tracks/appnexus-mobile-sdk-ios,appnexus/mobile-sdk-ios,8tracks/appnexus-mobile-sdk-ios,8tracks/appnexus-mobile-sdk-ios